Investigations into Athlon X2 Overclocking
by Jarred Walton on December 21, 2005 12:00 PM EST- Posted in
- CPUs
System Settings
One of the key factors for a successful overclock is choosing memory timings and speeds that will work. It is also necessary to tweak the HyperTransport speed and multiplier. We took screenshots in CPU-Z showing the CPU and Memory tabs, which will give some details on each configuration that we benchmarked. The images from CPU-Z are available in a single Zip file (1 MB) if you want to see them (they will not be shown elsewhere in this article).
Most of the changes that we made in the BIOS are pretty simple, and while DFI provided the option to tune many memory timings, we stuck with the options that are available on the majority of enthusiast motherboards. We modified multipliers, RAM ratios, voltages, and the standard memory timings: CL, tRCD, tRP, tRAS, and CMD. All other memory timings were left at Auto. If you have a motherboard that doesn't support the same settings that we used, you will need to use some trial and error to discover the optimal settings for your board.
Note how CPU voltages scaled rapidly as we neared the highest overclock levels. We did spend more time checking out voltages for this article, and unless a configuration could run through both 3DMark and both PCMark tests in sequence without crashing, we did not consider the voltage stable. We increased the voltage in 0.025V increments until the Futuremark tests all ran to completion.
While the Venice chip that we tested was fully stable at 2.7 GHz and slightly flaky at 2.8 GHz, the Manchester core that we used was slightly less capable. 2.6 GHz presented no problems at all during testing, and we ran Prime95, SuperPi, Folding@Home, and many games with the system running at 2.6 GHz without any crashes. 2.7 GHz was a different story, with periodic crashes in several games, particularly after an extended period of time. Prime95 and Folding@Home also experienced problems with the 2.7 GHz clock speed, though SuperPi still managed to calculate 32M decimals simultaneously on both cores. Other X2 chips may perform substantially better, or possibly worse, and better CPU cooling may provide a solution. (We've heard of some 2.8+ GHz overclocks - we could barely get into Windows at 2.8 GHz, and even sitting idle the PC would still crash.)
Again, this article presents results merely as a guideline, and depending on the components used, you will almost certainly need to change a number of settings in the BIOS. A crash in many ways is the best result possible - it means that you are definitely unstable. While passing the entire benchmark suite suggests that a system is stable, there is still no guarantee that a future application won't cause problems.
RAM timings and speed are the other items that we changed quite a bit. We kept the value RAM at a constant 2.5-3-3-7-1T 2.6V setting while adjusting the ratio to keep the speed at or below DDR400. The PC-4800 RAM only required minor adjustments to reach up to DDR-540, and we left the voltage at a constant 2.8V (2.75V was the BIOS reading - the RAM voltage setting was always around 0.05V higher than the measured value). Voltage for the VX was the maximum 3.2V that the motherboard could supply, and even then, it was insufficient at higher bandwidths to allow 2-2-2-7-1T timings. Something like a DFI LanParty should be able to achieve even better timings at overclocked settings with a 3.5 V setting, though OCZ VX and Mushkin Redline are becoming difficult to find, so perhaps it's a moot point. Finally, the Patriot 2GB sticks were good for up to DDR-480 speeds, give or take, with 2.5-3-3-8-1T timings. 2.7V appeared to provide the best results, with 2.8V perhaps helping slightly at the highest RAM speeds. The PDP RAM was able to remain slightly ahead of the value RAM in terms of timings and speed, while of course offering twice as much RAM.
One area where we experienced serious problems was in running with four DIMMs. First, as expected, a 2T command rate was required. Even then, using four OCZ EL Platinum DIMMs, we were only able to complete benchmarks at 2-3-2-7-2T timings (2.8V) at default CPU clock speed. All attempts to get the system to run stable in any overclocked state of 2200 MHz or more met with failure. Winstones could run successfully in almost every instance, including 2.5-4-4-8-2T timings at 2700 MHz, but Battlefield 2, Far Cry, and FEAR all crashed (hard-locked the PC) repeatedly. Test #5 in MemTest86 also failed with display corruption. Attempts to tune the RAM better met with limited success. By changing the EQ Drive Strength to "Weak", we were able to get further in testing, but nothing was truly stable. We would venture to say that the RAM is not to blame, as both pairs of DIMMs worked separately. The most likely culprits are the motherboard and BIOS, which are not as highly tuned as many enthusiast motherboards.
A last comment is that we didn't fully benchmark all of the settings listed in the charts. We tested 2000, 2200, 2400, 2600, and 2700 MHz. In order to provide a linear scale (so that the results at 2700 MHz aren't skewed), we interpolated the in-between scores. This is a problem with the graphing capability that we have within Excel. Basically, ignore results at 2100, 2300, and 2500 MHz - you could probably get scores within a few percent of what shows up on the graphs, but we didn't actually verify this.
One of the key factors for a successful overclock is choosing memory timings and speeds that will work. It is also necessary to tweak the HyperTransport speed and multiplier. We took screenshots in CPU-Z showing the CPU and Memory tabs, which will give some details on each configuration that we benchmarked. The images from CPU-Z are available in a single Zip file (1 MB) if you want to see them (they will not be shown elsewhere in this article).
Most of the changes that we made in the BIOS are pretty simple, and while DFI provided the option to tune many memory timings, we stuck with the options that are available on the majority of enthusiast motherboards. We modified multipliers, RAM ratios, voltages, and the standard memory timings: CL, tRCD, tRP, tRAS, and CMD. All other memory timings were left at Auto. If you have a motherboard that doesn't support the same settings that we used, you will need to use some trial and error to discover the optimal settings for your board.
Click to enlarge.
Note how CPU voltages scaled rapidly as we neared the highest overclock levels. We did spend more time checking out voltages for this article, and unless a configuration could run through both 3DMark and both PCMark tests in sequence without crashing, we did not consider the voltage stable. We increased the voltage in 0.025V increments until the Futuremark tests all ran to completion.
While the Venice chip that we tested was fully stable at 2.7 GHz and slightly flaky at 2.8 GHz, the Manchester core that we used was slightly less capable. 2.6 GHz presented no problems at all during testing, and we ran Prime95, SuperPi, Folding@Home, and many games with the system running at 2.6 GHz without any crashes. 2.7 GHz was a different story, with periodic crashes in several games, particularly after an extended period of time. Prime95 and Folding@Home also experienced problems with the 2.7 GHz clock speed, though SuperPi still managed to calculate 32M decimals simultaneously on both cores. Other X2 chips may perform substantially better, or possibly worse, and better CPU cooling may provide a solution. (We've heard of some 2.8+ GHz overclocks - we could barely get into Windows at 2.8 GHz, and even sitting idle the PC would still crash.)
Again, this article presents results merely as a guideline, and depending on the components used, you will almost certainly need to change a number of settings in the BIOS. A crash in many ways is the best result possible - it means that you are definitely unstable. While passing the entire benchmark suite suggests that a system is stable, there is still no guarantee that a future application won't cause problems.
RAM timings and speed are the other items that we changed quite a bit. We kept the value RAM at a constant 2.5-3-3-7-1T 2.6V setting while adjusting the ratio to keep the speed at or below DDR400. The PC-4800 RAM only required minor adjustments to reach up to DDR-540, and we left the voltage at a constant 2.8V (2.75V was the BIOS reading - the RAM voltage setting was always around 0.05V higher than the measured value). Voltage for the VX was the maximum 3.2V that the motherboard could supply, and even then, it was insufficient at higher bandwidths to allow 2-2-2-7-1T timings. Something like a DFI LanParty should be able to achieve even better timings at overclocked settings with a 3.5 V setting, though OCZ VX and Mushkin Redline are becoming difficult to find, so perhaps it's a moot point. Finally, the Patriot 2GB sticks were good for up to DDR-480 speeds, give or take, with 2.5-3-3-8-1T timings. 2.7V appeared to provide the best results, with 2.8V perhaps helping slightly at the highest RAM speeds. The PDP RAM was able to remain slightly ahead of the value RAM in terms of timings and speed, while of course offering twice as much RAM.
One area where we experienced serious problems was in running with four DIMMs. First, as expected, a 2T command rate was required. Even then, using four OCZ EL Platinum DIMMs, we were only able to complete benchmarks at 2-3-2-7-2T timings (2.8V) at default CPU clock speed. All attempts to get the system to run stable in any overclocked state of 2200 MHz or more met with failure. Winstones could run successfully in almost every instance, including 2.5-4-4-8-2T timings at 2700 MHz, but Battlefield 2, Far Cry, and FEAR all crashed (hard-locked the PC) repeatedly. Test #5 in MemTest86 also failed with display corruption. Attempts to tune the RAM better met with limited success. By changing the EQ Drive Strength to "Weak", we were able to get further in testing, but nothing was truly stable. We would venture to say that the RAM is not to blame, as both pairs of DIMMs worked separately. The most likely culprits are the motherboard and BIOS, which are not as highly tuned as many enthusiast motherboards.
A last comment is that we didn't fully benchmark all of the settings listed in the charts. We tested 2000, 2200, 2400, 2600, and 2700 MHz. In order to provide a linear scale (so that the results at 2700 MHz aren't skewed), we interpolated the in-between scores. This is a problem with the graphing capability that we have within Excel. Basically, ignore results at 2100, 2300, and 2500 MHz - you could probably get scores within a few percent of what shows up on the graphs, but we didn't actually verify this.
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rekabwolrab - Friday, February 24, 2006 - link
I'm new to OC and both the articles were very nice. Good Job. I am looking forward to the next installment with HSF/Cooling.shoeish - Friday, February 24, 2006 - link
Any results to share about watercooling or stock HSF with this chip yet?mcpdigital - Wednesday, December 28, 2005 - link
This article comes in the right moment since lots of people are thinking about upgrading their PCs or just did it.In my case I have a pretty simmilar configuration with LanParty Ultra-D, 3800 X2 and OCZ EL 3200 (2x1GB).
I found the breakeven of my setup at 280x9(2520), Mem at 210 MHz CAS 2,3,3,5 1T and HT x 3. Memory is running at its best, with 1T, Fastest in BIOS and CAS2 achieving around 61000 MB/s transfer rate running Sandra 2005 Pro, a value that is a bit under the maximum bandwidth with HT @1680 MHz of 6720MB/s
Anything over this speed makes the system unstable and requires a lot of slowdowns in other settings, voltage and temps raising fast, its a bad tradeoff IMO.
So Anandtech simple of the 3800 X2 seems a little better than mine, not that I'm not happy, I'm for sure.
Marcelo
Some1ne - Sunday, December 25, 2005 - link
Re: If you have any specific requests or suggestions before then, let me know.I noticed that as you increased the clock speed, you also increased your chipset voltage in a fairly linear way. I question whether or not this is really necessary or beneficial. I have a MSI Neo4 Platinum mainboard, and I've never had to touch the chipset voltage when overclocking. In fact, some of the behavior I observed when playing with it seemed to imply that the chipset got slightly less stable with higher voltages (though I didn't do enough testing to know conclusively if the relationship holds or not). Using the stock chipset voltage, I was able to hit:
2464 MHz (352x7) on a Winchester 3000+ w/ 6.6% over-VID on the CPU
2420 MHz (242x10) on a Manchester 3800+ w/ 10% over-VID on the CPU
2400 MHz (400x6) on a Winchester 3000+ w/ 6.6% over-VID on the CPU, just to see if the board would run stably at a 400 MHz "fsb" setting...it did
So as far as I can tell, boosting the chipset voltage is not necessary in order to attain a good overclock. It might be interesting if you could do tests to see what, if any, impact it has on stability at higher clock speeds, or maybe at least re-run your 2.7 GHz tests with stock chipset voltage just to make sure that your instability wasn't coming from an overheating chipset.
JarredWalton - Monday, December 26, 2005 - link
The results reported are only after testing all of the lower voltages. I encountered instability without the increased voltage to the chipset and processor. That said, other motherboards may not behave the same. I intend to switch to a different motherboard for the cooling tests -- a DFI LanParty SLI-DR. I will be sure to comment on whether the voltage requirements change or not.AtaStrumf - Friday, December 23, 2005 - link
Just want to commend you for a really thorough article. I miss that from other AT editors as of late.I also agree that all that ultra high end memory with tight timings is an absolute overkill for all but the most rabid overclockers. This is especially true since Athlon got an on die memory controller and became Athlon64. Just get some good quality RAM that will get you to 220-233 MHz so you have some headroom with BIOS FSB/dividers settings, because generic usually craps out at 201-203 MHz (sad but true).
Visual - Thursday, December 22, 2005 - link
Fantastic article, folks!It really showed alot. Sure, as someone commented, using a better mobo might have been interesting... but after all its the CPU that is important here, and you made the differences in performace with varying oc well presented.
I have to say, this article showed a surprisingly high difference between memory types too. You did comment in the end that there wasn't much difference, but there are some cases where there is :) 3dMark05 is the extreme case i guess, and not "real world" enough to be worth the added price, but 15fps or more in a lot of games from going from generic to the PC4800 mem isn't bad too. Seriously, this article showed the importance of memory way clearer than any of your RAM roundups in the past.
What is still dissapointing is that the test didn't reach the near-3ghz ocs a lot of people are bragging with on some forums :p But this is a good thing in a way, as now there won't be any misled readers buying the chip and expecting unrealistic achievments. I'm still curious about what the chips can do at max though, so I'm looking forward to your stock/Chill tests :) Maybe comparison with both infinity and lanparty boards? Maybe trying out several chips so you can give us a somewhat more realistic max average oc? (Hehe, no, scratch that last one. I don't want AT going broke from buying out all the X2s, plus no matter how many chips you test, the readers' own luck will deviate from yours)
Visual - Thursday, December 22, 2005 - link
Oh hey, I want to add a bit but there is no edit feature. So here goes...The RAM difference is much higher than with the singlecore veince. This does match with the assumption that two cores would need (and benefit) more bandwidth. So it also brings hope that the move to AM2 and DDR2 will have an even further boost, atleast for the dualcores. I'm already drooling over an imaginary AM2 X2 oced with DDR2 800mhz ram or faster :p
JarredWalton - Thursday, December 22, 2005 - link
I would say the performance difference shown here (relative to Venice) is from two things. First, two cores can use more bandwidth, though most of these tests won't show that since they're single-threaded. Second, the faster graphics card allows the CPU to really stretch its legs.Once you're at realistic settings for this system (minimum 1280x1024 resolution), the scores get a lot closer. Also, 3DMark has a pretty large deviation between runs - probably 3% or so. I didn't run 3DMark multiple times looking for the best score, so the results may not present a completely accurate representation of performance. Still, the CPU tests do show generic RAM at a pretty major disadvantage as clock speed increases. If 3DMark05's CPU test is an accurate estimate of multithreaded game performance, we're looking at a 25% difference! But I wouldn't put too much stock in 3DMark05. :p
Visual - Friday, December 23, 2005 - link
From what I read on the futuremark forums once, even though 3dmark05 is multithreaded, vertex processing in cpu tests is singlethreaded (some dx9 functionality from MS, not developed by futuremark) so isnt taking full advantage of dualcores still.