BIOS Settings

Once everything is working properly and you're sure that the PC doesn't have any problems, it's time to approach the actual process of overclocking. You might want to give the PC a few days of heavy use (system burn-in) just to be sure that it's stable. All of the FutureMark benchmarking utilities are a good start for stress testing a system, and if you buy the registered versions, you can set them to loop continually - at least, the 3DMark versions can be looped; a quick batch file will get the PCMark applications to loop as well. If you can loop 3DMark03/05 and PCMark04/05 for several days, you can be relatively sure that the computer is running stable. We'll use that same approach later to stress test our overclocked configurations.

Here's where things get more complex, and virtually every motherboard BIOS is going to be at least slightly different from what we present here. If you have a socket 939 motherboard, you'll need to refer to its manual (or figure out where the settings are on your own), but most of the names and/or values will be similar to what DFI uses. The key areas that will need adjustment for overclocking are the CPU bus speed, CPU multiplier, HyperTransport (HT) multiplier, memory speed, memory timings, and voltages for RAM, CPU, chipset, etc. Let's cover each of these quickly to explain the process. We'll include BIOS images from our particular motherboard, so you can look for the matching setting in whatever board you're using.


Click to enlarge.

Ignoring RAM for the moment, the way you overclock on Athlon 64 processor is simple enough. The normal clock speed is achieved by running a 200 MHz CPU bus frequency with the maximum CPU multiplier. Our 3200+ Venice has a 10X multiplier, so 10 X 200MHz = 2000MHz. If we increase the CPU bus to 270MHz and leave the multiplier at 10X, we'll have a 2700MHz CPU (provided that we can actually get that to run stably). Because Athlon 64 chips are all unlocked downwards on the multiplier, other combinations of CPU bus speed and multiplier are possible. 10x240, 9x267, and 8x300 will all run the CPU at around 2400MHz, resulting in similar performance. Note that we say "similar" but not "identical" performance: the RAM and other areas of the system will not be running at the same speed, so depending on how the other aspects influence performance, there could be a slight to moderate difference in overall performance.

The CPU bus speed is also referred to by other names. The DFI board labels it "CPU Frequency", while you may find HyperTransport Frequency in many BIOSes. (Some people will also call it the "Front Side Bus speed", which is not technically correct.) CPU Frequency, CPU Bus, HT Bus, etc. all mean the same thing, as the CPU communicates over an HT bus. Along with the CPU multiplier, there is also a HT multiplier (also called LDT - Lightning Data Transport - multiplier in some BIOSes). Most socket 939 motherboards support a 1000MHz HT speed, which is a 5X HT multiplier with a 200MHz base clock. The HyperTransport bus is sensitive to overclocking, so we need to keep its total speed in check. You may be able to run the HT bus at over 1000 MHz, but depending on motherboard and cooling, you will begin to have problems beyond a certain point. We'll keep our HT bus speed at or below 1050MHz by adjusting the HT multiplier as we increase the CPU bus speed (and we may at times drop lower if that brings stability). We can use the 4X multiplier with up to a 260MHz bus, and 3X will get us up to a 350MHz CPU bus (which is more than what most people are likely to reach, and more than what we'll test in this particular article). It is also possible to adjust the width of the HT bus from 16-bits up and down to 8-bits, but rarely does that help stabilize an overclock, so we'll leave it at 16/16.

We've covered the CPU and HT speed adjustments, but there's more to it than simply picking a target clock speed. In order to reach a stable overclock, you will often need additional voltage to the CPU and chipset - which affects the CPU speed and HT bus speed respectively. The default voltage of our Venice chip is 1.300V, but we will definitely increase the voltage as we go beyond a 10% overclock. Extreme overclocking (with liquid Nitrogen or phase change cooling) might go so far as to double the CPU voltages, but on air cooling that would be disastrous (not to mention few if any motherboards would even support that in the first place). We'll report the voltages required for each setting later on, but there are really two voltages: what we set in the BIOS, and what we actually get from the system. They may or may not be the same.

Something else that you should disable while in the BIOS is the Cool 'n Quiet feature of the Athlon 64. As that alters CPU voltage and multipliers dynamically in response to demand, it doesn't usually agree with overclocking. We also disable video and BIOS caching, as those are more relics of the DOS era than useful features (as far as we're aware). If you're interested in seeing the default settings that we used on the remaining BIOS screens, we have all the BIOS screens available for download in a Zip file.

System Assembly RAM BIOS Settings
Comments Locked

101 Comments

View All Comments

  • Powered by AMD - Monday, October 3, 2005 - link

    Do not forget The Athlon XP 1700+ 1.5Volts, DLT3C, mines is OC from 1467 Stock to 2250 Mhz and pretty cool with an old Thermaltake Blower...
    It can ever reach 2450 Mhz but with 1.8 Volts.
    hey, at 2250 Mhz its a 53% OC too!!
    Great article but it will be useful for me only when I need an Athlon 64 :p
  • donkeycrock - Monday, October 3, 2005 - link

    i noticed that frys is selling x-connect (500 Watts)psu for 25 dollars after rebate. it is extremely heavy, and not many reviews say if they are very good PSU's for overclocking, anybody have knowladge about this PSU.

    thanks
    brad
  • cryptonomicon - Monday, October 3, 2005 - link

    nice article jarred, and you worded the disclaimers perfectly, bravo.

    and its nice to see those ram comparisons. good to see those results on the latest a64 platform and confirm once again that the ram makes only a few percentage points difference, if that. shelling out all your dough on a good GPU, then buying the lowest model venice, a DFI board, and value ram is the way to go.
  • Googer - Monday, October 3, 2005 - link

    http://www2.amd.com/us-en/assets/content_type/Down...">AMD Thermal Grease List PDF
  • RupertS - Wednesday, October 26, 2005 - link

    Interesting, AMD only recommends thermal grease for short term use 'where the heat sink is removed and attached multiple times over a short period'. They definitely do not recommend it for long term use.
  • StriderGT - Monday, October 3, 2005 - link

    Both me, Zebo and many others have clarified long time ago in Anands forum the pointless struggle of purchasing extreme memory parts in Athlon64. Dividers and value ram will do the trick of excellent ocing giving you 95%++ of the performance someone gets with expensive and overvolted ram modules. Nice seeing anandtech come up with an article backing up the threads like this one (http://forums.anandtech.com/messageview.aspx?catid...">http://forums.anandtech.com/messageview...mp;threa...

    PS For those owning MSI Neo3 m/bs -and even the rest- I have created back then an excel calculating the actual memory frequency with the various BIOS settings. Enjoy
    http://www.geocities.com/gtstrider/">http://www.geocities.com/gtstrider/
  • JarredWalton - Monday, October 3, 2005 - link

    Yeah, I've seen quite a few threads around the 'net on this, but AT hadn't covered it very well, and I hoped to get something "official" out there. (None of the enthusiast sites have really covered this that well, as far as I could see.) Since I've been fooling around with various AMD CPU overclocks for a year now, I figured others might like to see the possibilities. High-end, high-cost is well and good for dreams, but like most people I live a bit closer to reality. $200 is about as much as I'm willing to pay for a CPU in most cases.
  • andyc - Monday, October 3, 2005 - link

    So you can basically overclock the 3000 to the same speeds the 3200 can? So it's not even worth it to go with the 3200?
  • JarredWalton - Monday, October 3, 2005 - link

    Well, perhaps. 9x300 requires a better motherboard than 10x270, though most boards than can handle 270 MHz CPU bus speeds will also handle 300 I think. For value overclockers, though, I don't think I'd bother spending the extra $50 on the 3200+, no. Spend it on the GPU instead (if you play games).
  • Mogadon - Monday, October 3, 2005 - link

    Great article Jarred, thanks for putting in all the hard work and time.

    I have one question regarding voltages. As I understand it, you wouldn't recommend running a VCore above 1.65V for a long term overclock. I understand the warnings and possible effects on the CPU with running a high VCore but I wanted to know if this is around the VCore that you would run on, say, your overclocked system?

    The majority of people on the forums here don't really recommend going above 1.55V or 1.6V, i was wondering if you had any comments about this.

Log in

Don't have an account? Sign up now