Merc
March 27th, 2007, 10:40:18 AM
Beginners Guide To Overclocking
by Merc
Please note that overclocking your components has the potential to seriously damage them. Raising voltages and frequencies on CPU's, GPU's and RAM as well as buses, can destroy them. Know your equipment's limits and ranges before tweaking in BIOS. Know what voltage is considered safe for your CPU and RAM, they're all different. Also, be aware that overclocking will void the warranty on most PC equipment. Reading this guide is a primer for seeking more knowledge, it is NOT all you should read. Overclock at your own risk and realize that the numbers offered below may not be appropriate for your equipment and components
Okay, now that the scary stuff is over, let's move on the the fun stuff. This is a short guide that I hope will answer a few of the questions I had when I decided to get serious about overclocking. There are myriad websites and guides available that are written by folks who are much more adept than I at overclocking but I had a hard time trying to equate what those guides were saying to what I was seeing in my BIOS. Every guide speaks of dividers for RAM and FSB (Front Side Bus or Northbridge Chipset) but on the A8N SLI Deluxe there is no divider, nor is there a FSB. And just what is that HTT setting really for?
Trying to answer these questions, which are all integral to overclocking, led to several different responses of varying accuracy. After a lot of research, question asking in forums and testing on my part I believe that I can save you the time and trouble of doing the same while simultaneously clarifying just what is going on here. At least that is my desire. I also hope that this guide will give you the ability to get on those overclocking sites and ask pertinent questions and understand just what they are talking about.
This guide, as the title suggests, is aimed at the first time overclocker based on an A8N SLI board. Boards are all different and Intel procedures are very different from AMD but the basics are the same, as are the theories, which is what this guide is based on.
This guide is not for the advanced overclocker as the topics are covered here at a basic level. What I hope the reader can do is once he or she has read this guide they will be able to understand what the more advanced overclockers are talking about and effectively apply the advice to their systems. Overclocking is about system knowledge and really understanding what is going on inside your box.
Those folks out there that have worlds more knowledge than me, that read this guide, should feel free to post any thoughts they have regarding its accuracy. I hope they also post some of their knowledge below. As always, this is a work in progress and I am always happy to pick up some new ideas or correct erroneous thinking. So, without further ado, let’s have a go at it.
What Is Overclocking?
What is overclocking? Basically it is getting something for nothing. It is buying a 3800X2 that runs at 2.0GHZ for $295 and getting it to run faster than a 4600X2 that costs $547. Both use a Manchester core and both have 2 x 128 KB of L1 cache and 2 x 512KB of L2 cache but one runs at 2.0 GHZ and the other runs at 2.4GHZ. That $250+ premium buys you that extra 400MHZ of speed.
The why of it is hard to say as there are a lot of theories about why one chip goes to a 4600X2 and another goes to the 3800X2. Closer to the center of the wafer, Wednesday instead of Friday manufacturing date, market placement etc etc. Suffice it to say that almost all chips have some overhead built into them that allows you to overclock. Some are much better overclockers than others and these are the ones the rabid overclockers clamor after.
The 3800X2 is a perfect example of a great overclocking chip hitting the scene. It wasn’t on any AMD roadmaps presented to the marketplace and was only announced after Intel introduced a low priced, low end dual core CPU. Within a couple of weeks after Intel’s bombshell, the 3800X2 was announced and hit the streets very soon after. What caught the overclocking communities attention was that spec-wise it was identical to the much higher priced 4600X2. Same core, same cache, same everything but one leaves the fab clocked 400MHZ higher than the other and priced at $250+ more. IMHO the 3800X2 type was created simply to compete at the low-end of the market against Intel’s similar offering.
Regardless, the overclocking community is the winner here as they got a very strong chip at a very low price. There are lots of other chips out there that are strong overclockers and new ones arrive on the scenes regularly so peruse the overclocking forums and watch for them if you are in the market to purchase a new CPU.
How to overclock on the A8N SLI Deluxe
How to overclock on the A8N SLI Deluxe is what I want to cover below. I won’t cover every little aspect of the art of overclocking. That would take a book. Nor do I have the expertise but I want this guide to give the reader the ability to go onto the overclocking sites and speak the lingo as it pertains to the A8N SLI Deluxe.
First of all, there are some terms one needs to understand in order to overclock. This guide is written for the A8N SLI Deluxe board and its Award BIOS, specifically, but most of it will be applicable to all A8N SLI boards as well as other 939 socket boards.
Front Side Bus (FSB)
Let’s start with the Front Side Bus (FSB) or Northbridge: On most boards there is a FSB that is the gateway to the RAM and other high priority components like the AGP or PCIe video port. On the FSB, or Northbridge, resides the memory controller that determines the speed at which data is transferred back and forth between the CPU and the RAM as well as other high-speed components such as the video card.
Setting this FSB speed is the heart and soul of overclocking. Everything else runs from this base speed via multipliers. Balancing components across the FSB is what you do when you overclock.
There is one problem here for socket 939 owners; there is no setting for FSB. Why? Because there is no FSB on 939 boards, according to the accepted definition of that term. AMD 64 CPU’s don’t use a FSB because the memory controller has been moved from the Northbridge chip (FSB) to onboard the CPU itself (one reason why AMD mobos are cheaper than Intel mobos). The AMD 64 CPU communicates directly with the RAM via a Hyper Transport (HT) link or, as it used to be called, a Lightning Data Transport link (the old name for basically the same thing). Read here for more info:
http://www.hypertransport.org/ HT is an extremely low latency, high bandwidth interconnect between two chips. It is why AMD has such high “FSB” speeds as compared to Intel CPU’s.
Given today’s components you cannot saturate this link. It is built for much bigger things coming in the future, but you still need to control the speed that it operates or you’ll overwhelm your components. So how do you set this “FSB” or base speed? In BIOS, on the A8N, you go to “Jumperfree” under Advanced Settings and set the speed at the CPU Freq line. I’ll explain below in more detail below.
There are just a couple of places that you’ll go to overclock. Both are under Advanced Settings in BIOS. The first is named CPU and is right at the top. To further confuse you there really aren’t any CPU settings in there. The second is Jumperfree Settings and this is where the real action starts.
ADVANCED SETTINGS: Jumperfree
Jumperfree is where the action takes place in overclocking. In here you set the FSB speed, the Vcore and Vdimm as well as PCI bus and PCIe speeds. As explained above there is no real FSB on the 939 socket mobos so the Award BIOS has, instead, a setting called CPU freq.
CPU Freq is interchangeable with FSB and from here on out I will refer to it as such, when pertinent. Setting CPU freq, or FSB, is the basis for every other setting we make in overclocking. Everything else multiplies from this number and we set voltages to compensate for an aggressive setting here. This is the number we play with the most. It is a straightforward setting increasing in 1 MHZ increments. How it interacts with everything else is what is important. Think of CPU freq, or FSB, as the base speed setting for the entire system. Some terms and how they interact with the FSB number will illustrate the importance of FSB and how everything works in overclocking:
MULTIPLIER:You’ll find two multipliers on the A8N SLI Deluxe. One is the CPU multiplier under Jumperfree and the other is the HTT multiplier under CPU. CPU Multiplier controls the CPU speed and the HTT multiplier controls the Hyper Transport Link and will be explained in the CPU Settings section.
HTT and the CPU use multipliers to get their actual operating freq from the FSB speed. RAM uses a divider and is explained in the next section also. All AMD 64 CPU’s come with the FSB speed set to 200MHZ and get to the actual operating frequency of the CPU with a multiplier. A 2.6GHZ or 2600MHZ CPU will have a 13x multiplier (13 x 200MHZ = 2600MHZ or 2.6GHZ) and a 2.2 GHZ or 2200MHZ CPU will have an 11X multiplier (11 x 200MHZ = 2200MHZ or 2.2GHZ). FX CPU’s are the only CPU’s where you can go up on the multiplier. The rest are capped and you can only go down.
You may want to change a multiplier from say 11X to 10X to get the FSB a little higher while leaving your CPU running at what you have found to be its top end speed. This would be helpful in getting a little more speed from RAM on a 5/4 divider (explained below) while leaving the CPU alone.
VOLTAGE: Please be advised that the below is how my non-electrical engineering mind pictures things, so it may not be technically accurate but should give you a good enough idea to understand what is going on.
Voltage is just as vital to overclocking as FSB speeds. Think of the voltage running through your system as a squared sine wave. Your household uses 60HZ AC (US) so you’ll have a 60HZ sine wave or 60 peaks per second going above and below the 0 line.
Of course, PC’s use DC because it is much more accurately delivered and doesn’t alternate. Just hook up a voltmeter to your AC line and you’ll see that the 120v coming into your house shifts around. Plus it goes into the negative as it alternates. So cut off that below zero portion of the sine wave and you are close to the DC voltage curve. The PC uses a square wave versus the AC sine wave, as it is a digital DC signal. Think rather than the rolling hills signature you would see on an oscilloscope for AC, the DC voltage in a PC as a series of blocks, with slightly inward slanted sides, such as a long line of pyramids with their top half’s lopped off and all of the pyramids being of the same exact height and width with the same slope to the lines.
Height is the voltage and width is the frequency. The higher the lopped off pyramids, the higher the voltage, the more narrow the lopped off pyramids, the higher the frequency. Now, increase that pattern exponentially into the MHZ range and you have the voltage pattern for our systems. Everything is clocked off this rising and falling signal.
This is why Vcore, the voltage to your CPU core, is important in overclocking. I’ll explain why through an example. Your new Manchester core has a base Vcore of 1.35 volts. This means the voltage plateaus at 1.35v, then descends to zero and rises back up to 1.35v. Your system will set a threshold at say 1.32v and the area between 1.32v and 1.35v’s is the rising and falling clock cycle that we talk about all the time and from which your system sets the operating speed. You have a clear rise starting at 1.32v, which plateaus at 1.35v and then a clear descent, which ends at 1.32v again. DDR RAM reads and writes on both the up and down of this curve, hence, Double Data Rate.
Now lets increase that freq from 2000MHZ to 2200MHZ but leave the plateau at 1.35v. There are a lot more rises, plateaus and descents in the voltage curve now and they are necessarily closer together. Height hasn’t changed as the voltage still plateaus at 1.35v but width has decreased as the frequency has gone from 200MHZ to 2200MHZ. Things are getting crowded and the CPU and other parts need a clearly delineated rise, plateau and fall to time everything correctly. But we are still stable so no worries yet.
Now lets go to 2300MHZ. Boom, individual pyramids are so close together now that the system can no longer accurately see the rise, plateau and fall of the voltage and we get a system freeze or BSOD or any other of the myriad maladies of a bad overclock.
So what do we do to get that CPU speed up? Well, since things are too crowded between 1.32v and 1.35v lets raise the peak to 1.4v and set the threshold to 1.37v. Now things are spread out again and we have a clear rise, plateau and fall on the voltage curve. Of course there is more current running through the CPU and it’s at a faster rate so the temperature is going to rise accordingly but we have a good HSF (Heat Sink Fan) on top of the CPU to cool it and under stress our CPU is only hitting 40c, which is way below any critical numbers, so let’s go ahead and start cranking that freq up.
Of course, you’ll soon hit that freeze situation again and will, once again, have to raise the voltage. This cycle will continue until you hit the max frequency your CPU can physically accommodate or the max temp the CPU can take. In the latter case you can use an alternate cooling method like water of even phase change to keep the temps under control but every chip has a physical limit that it will hit eventually. Electron migration, quantum physics stuff and other big words that guys with 40-pound heads throw around, come into play and you can go no further with your CPU.
Remember, too high of a voltage can seriously damage your components as will too high of a temperature. Most systems will crash before you exceed the safety margin but there are no guarantees here, so one must be aware of what is safe and what isn’t. Every CPU core and stick of RAM has a maximum voltage it can safely take and you must know this voltage and stay well clear of it.
So now we have the FSB setting, a CPU multiplier and the Vcore all working together to get our system overclocked. Higher frequencies will eventually require higher voltages, which generate more heat. We can control our CPU’s freq by either raising or lowering the FSB speed or changing the multiplier. We still have a couple of other things here that enter into the equation, namely our RAM and our HTT.
With the above I hope that you have a better understanding of why Vcore and Vdimm, the voltage to your DIMM, is important and why. The numbers I used are for illustration purposes only and don’t bare any resemblance to real world numbers but you get the idea. Electrical engineers please feel free to post any inaccuracies and I’ll be glad to incorporate them.
PCI and PCIe- I won’t go to in-depth here as these two numbers are not that important to what we are doing. Both have more than enough throughput to handle any load required at their native settings and really shouldn’t be seriously overclocked. Generally I manually set PCI to 33.33 MHZ and PCIe to 101MHZ and don’t touch them again. Some folks try and overclock the PCIe bus but the results usually end ugily and the benefits are nonexistent.
ADVANCED SETTINGS: CPU
In CPU you’ll find the settings for your RAM timings and the HTT. Both are important but the RAM is the more controllable. I’ll go through both here in detail:
HTT = Hyper Transport Technology (or possibly Tunnel, your guess below please): A common misconception is that the HTT is really your FSB and controls the bus speeds for RAM and PCIe. It doesn’t. It isn’t a divider either. This setting controls you HT multiplier for the Northbridge Chip only, which means it controls the bus speed for your PCIe interfaces and a few other items. That’s it. The big one here is your two video cards. You want stability for those expensive items so keep HTT at or around 1000 and you’ll be OK. By 1,000 I mean your CPU Freq, or FSB, in Jumperfree multiplied by the HTT multiplier, which goes from 1X to 5X.
Example: 250MHZ CPU freq times a 4X HTT multiplier means a 1,000 FSB. GOOD. 250MHZ CPU freq times a 5X multiplier = 1250 FSB: Probably a crash. 250MHZ CPU Freq times a 3X HTT = 750 FSB: Slow but stable. Just be aware that the system doesn’t like the HT to be set to low either as this too may cause a crash.
If you understand the above let's take it obe step further. HTT provides a dedicated high speed low latency pathway for cuips to communicate with each other. It is fullly scalable from 1X such as your PCIe 1X slot to 16X such as your PCIe 16X slot. What makes it so powerful is that data can be transmitted both ways simultaneously on a HTT link since each link is a dedictaed data path unlike PCI where you share the data path.
So in effect the above 1,000MHZ speed is actually a 2,000MHZ speed since your components can talk simultaneously with each other. We should really say that in the above example our HTT is running at 250MHZ CPU freq times a 4X HTT times 2X (for dual direction commmunication) = 2,000 FSB
More info on HTT is available here http://www.hypertransport.org/tech/tech_faqs.cfm
DRAM settings: (Dynamic Random Access Memory):
Select Manual here and the whole RAM timing page opens up. This is where you set your RAM timings and divider. I spoke above about memory dividers and the seeming lack of a setting for Memory dividers on the A8N. Well, your memory dividers reside right at the top in the Max Memclock tab. I’ll explain how dividers work below but let’s look at what they are first.
In Max Memclock you set DDR400 or DDR333 or DDR500 etc. These are your dividers on the A8N SLI Deluxe. DDR400 is the 1:1 divider and everything else adds or subtracts from that. Remember that 200MHZ is the base setting for the FSB and DDR400 is actually working at 200MHZ, which is why it is called a 1:1 divider. If RAM and FSB are working at the same freq you have synchronous timing. It is important to know, here, that DDR400 is a divider and not the setting for your DDR-400 RAM per se. DDR-500 RAM, running on a DDR400 divider, is running at the FSB speed, not DDR400. If FSB is at 250MHZ and your Max Memclock is set at DDR400 your RAM is running at DDR 500 speeds (250MHZ x 2). More on this below.
The A8N SLI BIOS lets you select from DDR200 all the way up to DDR600 but lets stick with 1:1 and down as normally what we want to do is run our FSB faster than the RAM can handle, hence an asynchronous multiplier such as 5:4 or DDR333 will be used. Here is how the numbers work out:
Dividers (DFI LP Expert Bios View)
http://img78.imageshack.us/img78/6767/dscf13530qf4ae.jpg (http://imageshack.us)
DDR200 2:1 memory runs at 0.50 x FSB speed
DDR266 3:2 memory runs at 0.66 x FSB speed
DDR333 6:5 memory runs at 0.83 x FSB speed
DDR400 1:1 memory runs at 1.00 x FSB speed
DDR 433 13:14 memory runs at 1.08 x FSB speed
A divider works by taking the FSB speed, which is the speed that your HT links to RAM, and slows it down or speeds it up. It is important to recall that DDR stands for Double Data Rate. Your 512MB stick of Corsair XMS DDR400 PC3200 RAM is actually running at 200MHZ. Double Data Rate is what gives you the theoretical throughput of 400MHZ. It does this by writing and reading to the stick of RAM on both the up cycle and down cycle of the voltage curve, thereby giving you two reads per clock cycle or Double Data Rate.
Let’s Look At An Example
Let’s look at an example and I’ll explain how the divider works. Lets say that you install a stick of DDR400 RAM. That RAM can theoretically run at 200MHZ and DDR will give you the 400MHZ rated speed. Now, in CPU Freq (FSB) you set 220MHZ. Do you still set the Max Memclock to DDR400? No, not unless you have some really, really special chips on that stick of RAM or you can crank the Vdimm up high enough to overclock it. DDR400 is the 1:1 divider, remember, and by setting DDR400 you are telling the RAM to run at 220MHZ, the same as the FSB or 440DDR. Crash in most cases.
Actually, you’ll set the DDR333, the 5:4 divider, which will give the RAM a speed of 176MHZ or DDR352. That is well below the operating freq of the RAM and leaves you some headroom for faster FSB speeds. Remember I talked about going down in the multiplier for faster FSB speeds while leaving the CPU speed as set? Here is where you may want to do that. You can increase the FSB speed, decrease the CPU multiplier, leave the same divider and thereby get closer to 200MHZ on your RAM. It’s all a balancing act and yes, a calculator comes in handy.
Raising Vdimm, or DDR Voltage in BIOS, in Jumperfree works the same way as raising Vcore. Once again, know the limits as RAM will die quickly at too high of a Vdimm, it doesn’t have the built-in safeguards that CPU’s do. Raising Vdimm, like raising Vcore, will allow the RAM to operate at a higher frequency. Most high quality RAM is safe at 2.8Vdimm but check with the manufacturer.
It is always beneficial to run your RAM as close to 1:1 as possible with the FSB. This way you avoid bottlenecking a high-speed system at the RAM. There are ways to do this, which will be discussed at the end of this section when I talk a little about buying RAM.
As an aside, there is a lot of talk about dividers being irrelevant to performance with the AMD-64 series of CPU’s. Be this as it may all sticking as close as possible to 1:1 divider is the accepted practice in the overclocking community. Which side is right will be argued for awhile but I’d strive fto be as close to a 1:1 divider as possible in my overclock.
Ram Timings
RAM Timings are a subject unto themselves. OCZ and Corsair have video tutorials and lots of written pages on each and every timing, as does DFI Street, so I will refrain from getting too in-depth here.
There are two settings that have the most impact on performance. One is CAS (or Tcas in BIOS) and the other is Timing as in 1T or 2T. CAS stands for Column Address Strobe and is the setting for how many clock cycles it takes for the system to address the first column after a request is sent from the CPU. CAS latency is a good number to judge your RAM quality by, as the lower that number the faster your stick of RAM. Just remember that CAS 2 RAM may need to be set to CAS 2.5 for an AMD 64 chip. Read the fine print on the manufacturer’s website.
Timing can be set to 1T or 2T. This is important as it is the number of clock cycles the system will use to start the next round of CAS. 2T is 2 clock cycles before the process of addressing the RAM even begins so you really want to get to 1T and stay there if possible. There are more caveats for the AMD 64 regarding 1T, 2T timing.
Above we talked about how the AMD 64 has the memory controller onboard the CPU itself. Here is where that causes some problems. In the earlier AMD 64 chips the memory controller could access four sticks of dual sided RAM (512MB sticks and above are dual sided meaning they have chips on both sides of the PCB) at 333MHZ DDR and 2 T timing only. By using 4 sticks of dual sided RAM you were immediately sent to the poor performer’s penalty box. Two sticks of dual sided were not a problem however.
Later chips have worked on resolving this issue and the dual cores are advertised as capable of 400DDR 2T for four sticks of dual sided memory. I have seen guys get 1T with 4 sticks of dual sided. Of course their systems are tweaked to the extreme and any serious overclocking is a no-go at that point.
The lesson here is if you want to overclock then use just two sticks of RAM. Also, two sticks of 1024MB will not clock as fast as two sticks of 512MB. There are a lot more banks to address in the same timeframe, which slows things down.
One last thing regarding RAM. There is lots of RAM out there and price is all over the place. Low latency is the catchphrase and the big money stuff. A stick of extremely low latency RAM is generally manufactured with the best chips available so that the banks of memory can be accessed at extraordinarily fast rates.
Is it worth it? Well dozens of tests have shown that these extremely low latency sticks of RAM only garner a 1%-4% increase in performance over the more middle of the road stuff. If that small percentage increase in speed is important enough to you then it may be worth the extra $150 for two 512MB sticks. Will you notice this difference while playing BF2? Nope, you’ll really only see the increase in performance in benchmarks and some very specialized programs.
Lastly, what about the DDR500 stuff and what benefit do you get from that? These higher frequency sticks sacrifice low latency for higher frequencies. The benefit here is if you are planning on taking your FSB up to a very high frequency then you may need to get some of the DDR500 PC4000 stuff in order to have it run comfortably.
Remember back to our RAM dividers and the 3800X2 running at 200MHZ with a 10X multiplier? Now lets take that FSB up to 250 on a 10X multiplier. Your RAM would have to run at 250MHZ in order to keep up with the FSB on a 1:1 divider. Theoretically you could use a DDR 266 divider and run the DDR400 PC3200 RAM at that speed but you can see that you are bottlenecking your system at the RAM. It is always better to stay as close to the 1:1 divider as possible as stated earlier.
In the above case it would be advisable to get yourself a couple of sticks of DDR500 PC4000 RAM. And run it at DDR400 or the 1:1 divider. The CAS latency will probably be 3 but the frequency should make up for that.
If you’re running a CPU that is already clocked fairly high and therefore you don’t expect to overclock the FSB as much as in the above case then you should go for the DDR400 PC3200 of DDR433 PC 3500 stuff with the better latencies. As an example, lets take the 4600X2 from above. The FSB here is running at 200MHZ also but on a 13X divider. We probably shouldn’t expect to get that FSB up much higher than 215 before we start seeing problem since our CPU would be at nearly 2.8GHZ. In this case I’d go for the DDR433 PC3500 RAM and stick it on a DDR400 1:1 divider.
Is that clear as mud? LOL. Now that we have the whole gamut covered, let’s go through a simulated overclocking session and try and put all of the above together:
Simulated Overclocking Session
Remember all hardware is different so this isnt garanteed to work
Once again we have the 3800X2 mounted and stable at 200MHZ 10X 1.35Vcore and two sticks of DDR400 PC3200 Corsair XMS Twinx 1024 (2 x 512MB) Ram with a divider of DDR400 and Vdimm set to 2.7. We are at default settings across the board. AMD Dual Core driver is installed and the MS Dual Core patch applied. Cool and Quiet, Ntune and AI NOS have all been deleted, disabled. Just remove them completely from your system if possible as they are instability generators and hate to be left out of the fight. Probe is up so we can monitor temperatures so let’s go in and set everything to manual in BIOS and begin to overclock.
Lets raise the FSB (CPU Freq) to 210 and leave everything else at base. Reboot and the system comes up fine. Run SuperPI to 16m and it looks good. So let’s go back into BIOS and raise the FSB to 215. Reboot and system freezes at POST. OK, why? Well you can raise Vcore here or you can set the HTT to 4X or set the memory divider to DDR333 (5/4). Let’s set Vcore to 1.375 and reboot. System POSTS and windows loads. Woot. OK, run SuperPI to 16m and after 1.5 minutes you get an error. Hmm, well maybe the RAM is getting swamped so set Vdimm to 2.75v and reboot and now SuperPI runs like a champ.
Let’s go to 220 on FSB. System POSTs but Windows BSODs. Lets set HTT to 4X and reboot. OK it loads and SuperPI runs. 225 and no POST. I’m thinking RAM now so set DDR333 and it POSTs, windows loads and SuperPI runs. As you move the frequencies up the crashes will get harder to decipher and the adjustments will be more difficult to find. There are lots of different settings that are possible and must be tried and keeping a record helps track what you have tried and where to go next. A pencil, steno pad and calculator are necessary tools.
There are many ways to accomplish overclocking. Some guys take RAM right out of the picture by setting the divider to DDR166 and then see how high the CPU will go. They’ll then do the same to RAM and when both maxes are known they’ll balance them together. Others have different methods but you get the picture. Trial and error and keep records as you go along.
Testing:
After you have an aggressive overclock and everything is stable you need to stress the system with something like Prime or another program to make sure you have really hit all the numbers right and the system is happy, temps are good and you are stable at all loads. There are lot's of testing programs out there and in this topic there is a link to most of them provided by 4Qman. The good news is they are all free! I would suggest, at minimum, the following tests:
http://overclockerzforum.com/phpbb2/viewtopic.php?t=253
1. Test the ram after changes using Memtest86 via a bootable floppy. Too aggressive settings will cause memory to corrupt data and render your system inoperable. Memtest will see this and report errors. It doesn't guarantee your settings are good but it will tell you if they are bad.
2.Testing
4Qman suggests the following testing regimen:
When testing the overclock its always best to use more than 1 test, many regard the Prime code the best test. Mainly as Super PI may pass 32mb run but Prime may still fail.
I believe the best stage of testing a overclock is the following...
Memtest86 Test#5 & 8# - Super PI 32M - Prime 95
I use the above always running Super PI 32mb when testing Ram as it is very good at test.
I normally run memtest86 Test#5 for around 10-15minutes then go into windows and run a 32M super PI. If this completes fine I will run the system overnight with Prime95 Toucher Test.
A good game of BF2 will soon decide if your system is Solid. Smile Ive seen many get there systems solid in Test ie Super PI yet still crash under 3D load.
I agree with 4Qman that BF2 is almost the defacto tester of an overclock. It is such a buggy and sensitive program that any instability will crash it instantly.
OK this has gotten a lot longer than I wanted but I hope it has addressed those overclocking questions you may have had and that you will now have the ability to access overclocking sites and understand what the pros are talking about. As said at the start, this is a guide for beginners and should not be the only thing you go by. Go to the Overclocker Forums and read what they have to say and watch what they do. And as always, have fun, this is why we build our own.
I’d like to say thanks to Roderick and 4Q for helping with this guide and offering many valuable suggestions and Arlie for his proofreading services.
Updated 11 April 2006 By 4Qman
Added Divider Image
Colour Headings and some Txt
by Merc
Please note that overclocking your components has the potential to seriously damage them. Raising voltages and frequencies on CPU's, GPU's and RAM as well as buses, can destroy them. Know your equipment's limits and ranges before tweaking in BIOS. Know what voltage is considered safe for your CPU and RAM, they're all different. Also, be aware that overclocking will void the warranty on most PC equipment. Reading this guide is a primer for seeking more knowledge, it is NOT all you should read. Overclock at your own risk and realize that the numbers offered below may not be appropriate for your equipment and components
Okay, now that the scary stuff is over, let's move on the the fun stuff. This is a short guide that I hope will answer a few of the questions I had when I decided to get serious about overclocking. There are myriad websites and guides available that are written by folks who are much more adept than I at overclocking but I had a hard time trying to equate what those guides were saying to what I was seeing in my BIOS. Every guide speaks of dividers for RAM and FSB (Front Side Bus or Northbridge Chipset) but on the A8N SLI Deluxe there is no divider, nor is there a FSB. And just what is that HTT setting really for?
Trying to answer these questions, which are all integral to overclocking, led to several different responses of varying accuracy. After a lot of research, question asking in forums and testing on my part I believe that I can save you the time and trouble of doing the same while simultaneously clarifying just what is going on here. At least that is my desire. I also hope that this guide will give you the ability to get on those overclocking sites and ask pertinent questions and understand just what they are talking about.
This guide, as the title suggests, is aimed at the first time overclocker based on an A8N SLI board. Boards are all different and Intel procedures are very different from AMD but the basics are the same, as are the theories, which is what this guide is based on.
This guide is not for the advanced overclocker as the topics are covered here at a basic level. What I hope the reader can do is once he or she has read this guide they will be able to understand what the more advanced overclockers are talking about and effectively apply the advice to their systems. Overclocking is about system knowledge and really understanding what is going on inside your box.
Those folks out there that have worlds more knowledge than me, that read this guide, should feel free to post any thoughts they have regarding its accuracy. I hope they also post some of their knowledge below. As always, this is a work in progress and I am always happy to pick up some new ideas or correct erroneous thinking. So, without further ado, let’s have a go at it.
What Is Overclocking?
What is overclocking? Basically it is getting something for nothing. It is buying a 3800X2 that runs at 2.0GHZ for $295 and getting it to run faster than a 4600X2 that costs $547. Both use a Manchester core and both have 2 x 128 KB of L1 cache and 2 x 512KB of L2 cache but one runs at 2.0 GHZ and the other runs at 2.4GHZ. That $250+ premium buys you that extra 400MHZ of speed.
The why of it is hard to say as there are a lot of theories about why one chip goes to a 4600X2 and another goes to the 3800X2. Closer to the center of the wafer, Wednesday instead of Friday manufacturing date, market placement etc etc. Suffice it to say that almost all chips have some overhead built into them that allows you to overclock. Some are much better overclockers than others and these are the ones the rabid overclockers clamor after.
The 3800X2 is a perfect example of a great overclocking chip hitting the scene. It wasn’t on any AMD roadmaps presented to the marketplace and was only announced after Intel introduced a low priced, low end dual core CPU. Within a couple of weeks after Intel’s bombshell, the 3800X2 was announced and hit the streets very soon after. What caught the overclocking communities attention was that spec-wise it was identical to the much higher priced 4600X2. Same core, same cache, same everything but one leaves the fab clocked 400MHZ higher than the other and priced at $250+ more. IMHO the 3800X2 type was created simply to compete at the low-end of the market against Intel’s similar offering.
Regardless, the overclocking community is the winner here as they got a very strong chip at a very low price. There are lots of other chips out there that are strong overclockers and new ones arrive on the scenes regularly so peruse the overclocking forums and watch for them if you are in the market to purchase a new CPU.
How to overclock on the A8N SLI Deluxe
How to overclock on the A8N SLI Deluxe is what I want to cover below. I won’t cover every little aspect of the art of overclocking. That would take a book. Nor do I have the expertise but I want this guide to give the reader the ability to go onto the overclocking sites and speak the lingo as it pertains to the A8N SLI Deluxe.
First of all, there are some terms one needs to understand in order to overclock. This guide is written for the A8N SLI Deluxe board and its Award BIOS, specifically, but most of it will be applicable to all A8N SLI boards as well as other 939 socket boards.
Front Side Bus (FSB)
Let’s start with the Front Side Bus (FSB) or Northbridge: On most boards there is a FSB that is the gateway to the RAM and other high priority components like the AGP or PCIe video port. On the FSB, or Northbridge, resides the memory controller that determines the speed at which data is transferred back and forth between the CPU and the RAM as well as other high-speed components such as the video card.
Setting this FSB speed is the heart and soul of overclocking. Everything else runs from this base speed via multipliers. Balancing components across the FSB is what you do when you overclock.
There is one problem here for socket 939 owners; there is no setting for FSB. Why? Because there is no FSB on 939 boards, according to the accepted definition of that term. AMD 64 CPU’s don’t use a FSB because the memory controller has been moved from the Northbridge chip (FSB) to onboard the CPU itself (one reason why AMD mobos are cheaper than Intel mobos). The AMD 64 CPU communicates directly with the RAM via a Hyper Transport (HT) link or, as it used to be called, a Lightning Data Transport link (the old name for basically the same thing). Read here for more info:
http://www.hypertransport.org/ HT is an extremely low latency, high bandwidth interconnect between two chips. It is why AMD has such high “FSB” speeds as compared to Intel CPU’s.
Given today’s components you cannot saturate this link. It is built for much bigger things coming in the future, but you still need to control the speed that it operates or you’ll overwhelm your components. So how do you set this “FSB” or base speed? In BIOS, on the A8N, you go to “Jumperfree” under Advanced Settings and set the speed at the CPU Freq line. I’ll explain below in more detail below.
There are just a couple of places that you’ll go to overclock. Both are under Advanced Settings in BIOS. The first is named CPU and is right at the top. To further confuse you there really aren’t any CPU settings in there. The second is Jumperfree Settings and this is where the real action starts.
ADVANCED SETTINGS: Jumperfree
Jumperfree is where the action takes place in overclocking. In here you set the FSB speed, the Vcore and Vdimm as well as PCI bus and PCIe speeds. As explained above there is no real FSB on the 939 socket mobos so the Award BIOS has, instead, a setting called CPU freq.
CPU Freq is interchangeable with FSB and from here on out I will refer to it as such, when pertinent. Setting CPU freq, or FSB, is the basis for every other setting we make in overclocking. Everything else multiplies from this number and we set voltages to compensate for an aggressive setting here. This is the number we play with the most. It is a straightforward setting increasing in 1 MHZ increments. How it interacts with everything else is what is important. Think of CPU freq, or FSB, as the base speed setting for the entire system. Some terms and how they interact with the FSB number will illustrate the importance of FSB and how everything works in overclocking:
MULTIPLIER:You’ll find two multipliers on the A8N SLI Deluxe. One is the CPU multiplier under Jumperfree and the other is the HTT multiplier under CPU. CPU Multiplier controls the CPU speed and the HTT multiplier controls the Hyper Transport Link and will be explained in the CPU Settings section.
HTT and the CPU use multipliers to get their actual operating freq from the FSB speed. RAM uses a divider and is explained in the next section also. All AMD 64 CPU’s come with the FSB speed set to 200MHZ and get to the actual operating frequency of the CPU with a multiplier. A 2.6GHZ or 2600MHZ CPU will have a 13x multiplier (13 x 200MHZ = 2600MHZ or 2.6GHZ) and a 2.2 GHZ or 2200MHZ CPU will have an 11X multiplier (11 x 200MHZ = 2200MHZ or 2.2GHZ). FX CPU’s are the only CPU’s where you can go up on the multiplier. The rest are capped and you can only go down.
You may want to change a multiplier from say 11X to 10X to get the FSB a little higher while leaving your CPU running at what you have found to be its top end speed. This would be helpful in getting a little more speed from RAM on a 5/4 divider (explained below) while leaving the CPU alone.
VOLTAGE: Please be advised that the below is how my non-electrical engineering mind pictures things, so it may not be technically accurate but should give you a good enough idea to understand what is going on.
Voltage is just as vital to overclocking as FSB speeds. Think of the voltage running through your system as a squared sine wave. Your household uses 60HZ AC (US) so you’ll have a 60HZ sine wave or 60 peaks per second going above and below the 0 line.
Of course, PC’s use DC because it is much more accurately delivered and doesn’t alternate. Just hook up a voltmeter to your AC line and you’ll see that the 120v coming into your house shifts around. Plus it goes into the negative as it alternates. So cut off that below zero portion of the sine wave and you are close to the DC voltage curve. The PC uses a square wave versus the AC sine wave, as it is a digital DC signal. Think rather than the rolling hills signature you would see on an oscilloscope for AC, the DC voltage in a PC as a series of blocks, with slightly inward slanted sides, such as a long line of pyramids with their top half’s lopped off and all of the pyramids being of the same exact height and width with the same slope to the lines.
Height is the voltage and width is the frequency. The higher the lopped off pyramids, the higher the voltage, the more narrow the lopped off pyramids, the higher the frequency. Now, increase that pattern exponentially into the MHZ range and you have the voltage pattern for our systems. Everything is clocked off this rising and falling signal.
This is why Vcore, the voltage to your CPU core, is important in overclocking. I’ll explain why through an example. Your new Manchester core has a base Vcore of 1.35 volts. This means the voltage plateaus at 1.35v, then descends to zero and rises back up to 1.35v. Your system will set a threshold at say 1.32v and the area between 1.32v and 1.35v’s is the rising and falling clock cycle that we talk about all the time and from which your system sets the operating speed. You have a clear rise starting at 1.32v, which plateaus at 1.35v and then a clear descent, which ends at 1.32v again. DDR RAM reads and writes on both the up and down of this curve, hence, Double Data Rate.
Now lets increase that freq from 2000MHZ to 2200MHZ but leave the plateau at 1.35v. There are a lot more rises, plateaus and descents in the voltage curve now and they are necessarily closer together. Height hasn’t changed as the voltage still plateaus at 1.35v but width has decreased as the frequency has gone from 200MHZ to 2200MHZ. Things are getting crowded and the CPU and other parts need a clearly delineated rise, plateau and fall to time everything correctly. But we are still stable so no worries yet.
Now lets go to 2300MHZ. Boom, individual pyramids are so close together now that the system can no longer accurately see the rise, plateau and fall of the voltage and we get a system freeze or BSOD or any other of the myriad maladies of a bad overclock.
So what do we do to get that CPU speed up? Well, since things are too crowded between 1.32v and 1.35v lets raise the peak to 1.4v and set the threshold to 1.37v. Now things are spread out again and we have a clear rise, plateau and fall on the voltage curve. Of course there is more current running through the CPU and it’s at a faster rate so the temperature is going to rise accordingly but we have a good HSF (Heat Sink Fan) on top of the CPU to cool it and under stress our CPU is only hitting 40c, which is way below any critical numbers, so let’s go ahead and start cranking that freq up.
Of course, you’ll soon hit that freeze situation again and will, once again, have to raise the voltage. This cycle will continue until you hit the max frequency your CPU can physically accommodate or the max temp the CPU can take. In the latter case you can use an alternate cooling method like water of even phase change to keep the temps under control but every chip has a physical limit that it will hit eventually. Electron migration, quantum physics stuff and other big words that guys with 40-pound heads throw around, come into play and you can go no further with your CPU.
Remember, too high of a voltage can seriously damage your components as will too high of a temperature. Most systems will crash before you exceed the safety margin but there are no guarantees here, so one must be aware of what is safe and what isn’t. Every CPU core and stick of RAM has a maximum voltage it can safely take and you must know this voltage and stay well clear of it.
So now we have the FSB setting, a CPU multiplier and the Vcore all working together to get our system overclocked. Higher frequencies will eventually require higher voltages, which generate more heat. We can control our CPU’s freq by either raising or lowering the FSB speed or changing the multiplier. We still have a couple of other things here that enter into the equation, namely our RAM and our HTT.
With the above I hope that you have a better understanding of why Vcore and Vdimm, the voltage to your DIMM, is important and why. The numbers I used are for illustration purposes only and don’t bare any resemblance to real world numbers but you get the idea. Electrical engineers please feel free to post any inaccuracies and I’ll be glad to incorporate them.
PCI and PCIe- I won’t go to in-depth here as these two numbers are not that important to what we are doing. Both have more than enough throughput to handle any load required at their native settings and really shouldn’t be seriously overclocked. Generally I manually set PCI to 33.33 MHZ and PCIe to 101MHZ and don’t touch them again. Some folks try and overclock the PCIe bus but the results usually end ugily and the benefits are nonexistent.
ADVANCED SETTINGS: CPU
In CPU you’ll find the settings for your RAM timings and the HTT. Both are important but the RAM is the more controllable. I’ll go through both here in detail:
HTT = Hyper Transport Technology (or possibly Tunnel, your guess below please): A common misconception is that the HTT is really your FSB and controls the bus speeds for RAM and PCIe. It doesn’t. It isn’t a divider either. This setting controls you HT multiplier for the Northbridge Chip only, which means it controls the bus speed for your PCIe interfaces and a few other items. That’s it. The big one here is your two video cards. You want stability for those expensive items so keep HTT at or around 1000 and you’ll be OK. By 1,000 I mean your CPU Freq, or FSB, in Jumperfree multiplied by the HTT multiplier, which goes from 1X to 5X.
Example: 250MHZ CPU freq times a 4X HTT multiplier means a 1,000 FSB. GOOD. 250MHZ CPU freq times a 5X multiplier = 1250 FSB: Probably a crash. 250MHZ CPU Freq times a 3X HTT = 750 FSB: Slow but stable. Just be aware that the system doesn’t like the HT to be set to low either as this too may cause a crash.
If you understand the above let's take it obe step further. HTT provides a dedicated high speed low latency pathway for cuips to communicate with each other. It is fullly scalable from 1X such as your PCIe 1X slot to 16X such as your PCIe 16X slot. What makes it so powerful is that data can be transmitted both ways simultaneously on a HTT link since each link is a dedictaed data path unlike PCI where you share the data path.
So in effect the above 1,000MHZ speed is actually a 2,000MHZ speed since your components can talk simultaneously with each other. We should really say that in the above example our HTT is running at 250MHZ CPU freq times a 4X HTT times 2X (for dual direction commmunication) = 2,000 FSB
More info on HTT is available here http://www.hypertransport.org/tech/tech_faqs.cfm
DRAM settings: (Dynamic Random Access Memory):
Select Manual here and the whole RAM timing page opens up. This is where you set your RAM timings and divider. I spoke above about memory dividers and the seeming lack of a setting for Memory dividers on the A8N. Well, your memory dividers reside right at the top in the Max Memclock tab. I’ll explain how dividers work below but let’s look at what they are first.
In Max Memclock you set DDR400 or DDR333 or DDR500 etc. These are your dividers on the A8N SLI Deluxe. DDR400 is the 1:1 divider and everything else adds or subtracts from that. Remember that 200MHZ is the base setting for the FSB and DDR400 is actually working at 200MHZ, which is why it is called a 1:1 divider. If RAM and FSB are working at the same freq you have synchronous timing. It is important to know, here, that DDR400 is a divider and not the setting for your DDR-400 RAM per se. DDR-500 RAM, running on a DDR400 divider, is running at the FSB speed, not DDR400. If FSB is at 250MHZ and your Max Memclock is set at DDR400 your RAM is running at DDR 500 speeds (250MHZ x 2). More on this below.
The A8N SLI BIOS lets you select from DDR200 all the way up to DDR600 but lets stick with 1:1 and down as normally what we want to do is run our FSB faster than the RAM can handle, hence an asynchronous multiplier such as 5:4 or DDR333 will be used. Here is how the numbers work out:
Dividers (DFI LP Expert Bios View)
http://img78.imageshack.us/img78/6767/dscf13530qf4ae.jpg (http://imageshack.us)
DDR200 2:1 memory runs at 0.50 x FSB speed
DDR266 3:2 memory runs at 0.66 x FSB speed
DDR333 6:5 memory runs at 0.83 x FSB speed
DDR400 1:1 memory runs at 1.00 x FSB speed
DDR 433 13:14 memory runs at 1.08 x FSB speed
A divider works by taking the FSB speed, which is the speed that your HT links to RAM, and slows it down or speeds it up. It is important to recall that DDR stands for Double Data Rate. Your 512MB stick of Corsair XMS DDR400 PC3200 RAM is actually running at 200MHZ. Double Data Rate is what gives you the theoretical throughput of 400MHZ. It does this by writing and reading to the stick of RAM on both the up cycle and down cycle of the voltage curve, thereby giving you two reads per clock cycle or Double Data Rate.
Let’s Look At An Example
Let’s look at an example and I’ll explain how the divider works. Lets say that you install a stick of DDR400 RAM. That RAM can theoretically run at 200MHZ and DDR will give you the 400MHZ rated speed. Now, in CPU Freq (FSB) you set 220MHZ. Do you still set the Max Memclock to DDR400? No, not unless you have some really, really special chips on that stick of RAM or you can crank the Vdimm up high enough to overclock it. DDR400 is the 1:1 divider, remember, and by setting DDR400 you are telling the RAM to run at 220MHZ, the same as the FSB or 440DDR. Crash in most cases.
Actually, you’ll set the DDR333, the 5:4 divider, which will give the RAM a speed of 176MHZ or DDR352. That is well below the operating freq of the RAM and leaves you some headroom for faster FSB speeds. Remember I talked about going down in the multiplier for faster FSB speeds while leaving the CPU speed as set? Here is where you may want to do that. You can increase the FSB speed, decrease the CPU multiplier, leave the same divider and thereby get closer to 200MHZ on your RAM. It’s all a balancing act and yes, a calculator comes in handy.
Raising Vdimm, or DDR Voltage in BIOS, in Jumperfree works the same way as raising Vcore. Once again, know the limits as RAM will die quickly at too high of a Vdimm, it doesn’t have the built-in safeguards that CPU’s do. Raising Vdimm, like raising Vcore, will allow the RAM to operate at a higher frequency. Most high quality RAM is safe at 2.8Vdimm but check with the manufacturer.
It is always beneficial to run your RAM as close to 1:1 as possible with the FSB. This way you avoid bottlenecking a high-speed system at the RAM. There are ways to do this, which will be discussed at the end of this section when I talk a little about buying RAM.
As an aside, there is a lot of talk about dividers being irrelevant to performance with the AMD-64 series of CPU’s. Be this as it may all sticking as close as possible to 1:1 divider is the accepted practice in the overclocking community. Which side is right will be argued for awhile but I’d strive fto be as close to a 1:1 divider as possible in my overclock.
Ram Timings
RAM Timings are a subject unto themselves. OCZ and Corsair have video tutorials and lots of written pages on each and every timing, as does DFI Street, so I will refrain from getting too in-depth here.
There are two settings that have the most impact on performance. One is CAS (or Tcas in BIOS) and the other is Timing as in 1T or 2T. CAS stands for Column Address Strobe and is the setting for how many clock cycles it takes for the system to address the first column after a request is sent from the CPU. CAS latency is a good number to judge your RAM quality by, as the lower that number the faster your stick of RAM. Just remember that CAS 2 RAM may need to be set to CAS 2.5 for an AMD 64 chip. Read the fine print on the manufacturer’s website.
Timing can be set to 1T or 2T. This is important as it is the number of clock cycles the system will use to start the next round of CAS. 2T is 2 clock cycles before the process of addressing the RAM even begins so you really want to get to 1T and stay there if possible. There are more caveats for the AMD 64 regarding 1T, 2T timing.
Above we talked about how the AMD 64 has the memory controller onboard the CPU itself. Here is where that causes some problems. In the earlier AMD 64 chips the memory controller could access four sticks of dual sided RAM (512MB sticks and above are dual sided meaning they have chips on both sides of the PCB) at 333MHZ DDR and 2 T timing only. By using 4 sticks of dual sided RAM you were immediately sent to the poor performer’s penalty box. Two sticks of dual sided were not a problem however.
Later chips have worked on resolving this issue and the dual cores are advertised as capable of 400DDR 2T for four sticks of dual sided memory. I have seen guys get 1T with 4 sticks of dual sided. Of course their systems are tweaked to the extreme and any serious overclocking is a no-go at that point.
The lesson here is if you want to overclock then use just two sticks of RAM. Also, two sticks of 1024MB will not clock as fast as two sticks of 512MB. There are a lot more banks to address in the same timeframe, which slows things down.
One last thing regarding RAM. There is lots of RAM out there and price is all over the place. Low latency is the catchphrase and the big money stuff. A stick of extremely low latency RAM is generally manufactured with the best chips available so that the banks of memory can be accessed at extraordinarily fast rates.
Is it worth it? Well dozens of tests have shown that these extremely low latency sticks of RAM only garner a 1%-4% increase in performance over the more middle of the road stuff. If that small percentage increase in speed is important enough to you then it may be worth the extra $150 for two 512MB sticks. Will you notice this difference while playing BF2? Nope, you’ll really only see the increase in performance in benchmarks and some very specialized programs.
Lastly, what about the DDR500 stuff and what benefit do you get from that? These higher frequency sticks sacrifice low latency for higher frequencies. The benefit here is if you are planning on taking your FSB up to a very high frequency then you may need to get some of the DDR500 PC4000 stuff in order to have it run comfortably.
Remember back to our RAM dividers and the 3800X2 running at 200MHZ with a 10X multiplier? Now lets take that FSB up to 250 on a 10X multiplier. Your RAM would have to run at 250MHZ in order to keep up with the FSB on a 1:1 divider. Theoretically you could use a DDR 266 divider and run the DDR400 PC3200 RAM at that speed but you can see that you are bottlenecking your system at the RAM. It is always better to stay as close to the 1:1 divider as possible as stated earlier.
In the above case it would be advisable to get yourself a couple of sticks of DDR500 PC4000 RAM. And run it at DDR400 or the 1:1 divider. The CAS latency will probably be 3 but the frequency should make up for that.
If you’re running a CPU that is already clocked fairly high and therefore you don’t expect to overclock the FSB as much as in the above case then you should go for the DDR400 PC3200 of DDR433 PC 3500 stuff with the better latencies. As an example, lets take the 4600X2 from above. The FSB here is running at 200MHZ also but on a 13X divider. We probably shouldn’t expect to get that FSB up much higher than 215 before we start seeing problem since our CPU would be at nearly 2.8GHZ. In this case I’d go for the DDR433 PC3500 RAM and stick it on a DDR400 1:1 divider.
Is that clear as mud? LOL. Now that we have the whole gamut covered, let’s go through a simulated overclocking session and try and put all of the above together:
Simulated Overclocking Session
Remember all hardware is different so this isnt garanteed to work
Once again we have the 3800X2 mounted and stable at 200MHZ 10X 1.35Vcore and two sticks of DDR400 PC3200 Corsair XMS Twinx 1024 (2 x 512MB) Ram with a divider of DDR400 and Vdimm set to 2.7. We are at default settings across the board. AMD Dual Core driver is installed and the MS Dual Core patch applied. Cool and Quiet, Ntune and AI NOS have all been deleted, disabled. Just remove them completely from your system if possible as they are instability generators and hate to be left out of the fight. Probe is up so we can monitor temperatures so let’s go in and set everything to manual in BIOS and begin to overclock.
Lets raise the FSB (CPU Freq) to 210 and leave everything else at base. Reboot and the system comes up fine. Run SuperPI to 16m and it looks good. So let’s go back into BIOS and raise the FSB to 215. Reboot and system freezes at POST. OK, why? Well you can raise Vcore here or you can set the HTT to 4X or set the memory divider to DDR333 (5/4). Let’s set Vcore to 1.375 and reboot. System POSTS and windows loads. Woot. OK, run SuperPI to 16m and after 1.5 minutes you get an error. Hmm, well maybe the RAM is getting swamped so set Vdimm to 2.75v and reboot and now SuperPI runs like a champ.
Let’s go to 220 on FSB. System POSTs but Windows BSODs. Lets set HTT to 4X and reboot. OK it loads and SuperPI runs. 225 and no POST. I’m thinking RAM now so set DDR333 and it POSTs, windows loads and SuperPI runs. As you move the frequencies up the crashes will get harder to decipher and the adjustments will be more difficult to find. There are lots of different settings that are possible and must be tried and keeping a record helps track what you have tried and where to go next. A pencil, steno pad and calculator are necessary tools.
There are many ways to accomplish overclocking. Some guys take RAM right out of the picture by setting the divider to DDR166 and then see how high the CPU will go. They’ll then do the same to RAM and when both maxes are known they’ll balance them together. Others have different methods but you get the picture. Trial and error and keep records as you go along.
Testing:
After you have an aggressive overclock and everything is stable you need to stress the system with something like Prime or another program to make sure you have really hit all the numbers right and the system is happy, temps are good and you are stable at all loads. There are lot's of testing programs out there and in this topic there is a link to most of them provided by 4Qman. The good news is they are all free! I would suggest, at minimum, the following tests:
http://overclockerzforum.com/phpbb2/viewtopic.php?t=253
1. Test the ram after changes using Memtest86 via a bootable floppy. Too aggressive settings will cause memory to corrupt data and render your system inoperable. Memtest will see this and report errors. It doesn't guarantee your settings are good but it will tell you if they are bad.
2.Testing
4Qman suggests the following testing regimen:
When testing the overclock its always best to use more than 1 test, many regard the Prime code the best test. Mainly as Super PI may pass 32mb run but Prime may still fail.
I believe the best stage of testing a overclock is the following...
Memtest86 Test#5 & 8# - Super PI 32M - Prime 95
I use the above always running Super PI 32mb when testing Ram as it is very good at test.
I normally run memtest86 Test#5 for around 10-15minutes then go into windows and run a 32M super PI. If this completes fine I will run the system overnight with Prime95 Toucher Test.
A good game of BF2 will soon decide if your system is Solid. Smile Ive seen many get there systems solid in Test ie Super PI yet still crash under 3D load.
I agree with 4Qman that BF2 is almost the defacto tester of an overclock. It is such a buggy and sensitive program that any instability will crash it instantly.
OK this has gotten a lot longer than I wanted but I hope it has addressed those overclocking questions you may have had and that you will now have the ability to access overclocking sites and understand what the pros are talking about. As said at the start, this is a guide for beginners and should not be the only thing you go by. Go to the Overclocker Forums and read what they have to say and watch what they do. And as always, have fun, this is why we build our own.
I’d like to say thanks to Roderick and 4Q for helping with this guide and offering many valuable suggestions and Arlie for his proofreading services.
Updated 11 April 2006 By 4Qman
Added Divider Image
Colour Headings and some Txt