Investigations into Socket 939 Athlon 64 Overclocking
by Jarred Walton on October 3, 2005 4:35 PM EST- Posted in
- CPUs
Introduction
Note: This article is an in-depth look at overclocking. We'll cover how to do it, what sort of performance you can achieve, problems and potential solutions, etc. Overclocking can be frustrating, rewarding, fun, and dangerous. We don't mean "burn the house down" dangerous, but you could certainly end up ruining some or all of your computer components. We take no responsibility for any difficulties or losses you may experience by using the information in this article, and we certainly take no responsibility for any damage that may occur to any person, place, or object. The manufacturers of the parts that we are using are also not accountable for any loss/damage that may occur - most companies void your warranty for overclocking. It's a risk, and it's your risk - proceed with caution. Finally, overclocking is never a "guaranteed result". You may or may not match the results that we achieve. We'll be happy to offer suggestions if you need them, as will many of our forum members. Patience and research are part of overclocking as well, so please understand that you may have to do some work on your own. If you can accept those warnings, we hope that you enjoy this article.
Back in the day, overclocking was in some ways simpler than what we see now. You would typically buy a mid-range processor and then try to increase the bus speeds as much as possible in order to get the most performance out of your system. Older Pentium chips also allowed you to change the multiplier, so with some luck, you might get your 2.5X multiplier on a Pentium 166 up to 3.0X, resulting in a 33 MHz overclock. Other than a few special chips like the Pentium M and Athlon FX, increasing multipliers is no longer possible. The modification of bus speeds can still be used, but it isn't necessarily the best or only way to try to overclock your system. We have mentioned overclocking performance in many articles, but we haven't taken the time to really explore all the options out there. We also know that current Intel and AMD setups have very different options and performance when overclocking is used, so we want to look at that as well.
Before we branch out into AMD vs. Intel comparisons, however, let's talk about the past top performers. The Celeron 300A is fondly remembered by many people, and with good reason. Yes, we have had some other good parts in the intervening years, like the 2.4 GHz Northwood cores, the low end Prescott cores, and the Athlon XP-M Barton parts. However, when you look at the 50% overclock of the Celeron 300A (and it wasn't just possible, it was common), none of the other parts have really ever approached that level of overclocking without some serious investment in cooling options. (Some people even managed to get the 300A to 504 MHz - an amazing 68% overclock!) Northwood's 2.4 GHz to 3.2 GHz is still an impressive 33% overclock. The 2.4 GHz to 3.6 GHz Prescott overclock (using the 2.4A) actually matches the 50% of the 300A, but you sacrifice some features (HyperThreading and high FSB speeds) with the lower model parts. Meanwhile, the overclocking darling that was the XP-M 2500+ "only" managed a typical overclock of 1.87 GHz to 2.4 GHz, a 29% overclock.
That brings us to the part that we're investigating today. It is arguably the best overclocking platform since the old Celeron 300A: AMD's Venice core. One thing that we didn't mention above is the role that price plays for many overclockers. Sure, the Athlon-FX can reach clock speeds and performance that most other chips only dream about, but at a cost of roughly $900 just for the processor, a lot of people will only read about it. What made the 300A so attractive was that it was not only a monster overclocking chip, but it cost around $150 and competed with $500 chips. That's why the 2.4C and 2.4A Pentium 4 are also well regarded; they cost under $200 and could compete with chips that cost two to three times as much. The price of entry for the cheapest Venice core (the 3000+) is once again very low; $120 for the OEM model, or $145 for the retail version.
We'll get into the details more in a moment, but for now, we'll just say that the 3200+ may actually be a better choice, and that's what we are using for this article. We are also using the retail model, and some people will say that retail parts tend to overclock better than the OEM chips. We'll simulate 3000+ overclocking using a 9X CPU multiplier, but that may or may not be an entirely accurate representation of 3000+ overclocking performance. In general, though, what we're hearing is that almost all of the Venice cores can run at very high clock speeds with a bit of effort, so there isn't a huge difference between 3000+ parts binned for 1.8 GHz and 3800+ parts binned for 2.4 GHz. AMD has simply set the package to use a maximum 9X multiplier on the former and a 12X multiplier on the latter. Talking about CPU multipliers leads us into the real meat of the discussion, though, so let's get into it.
Note: This article is an in-depth look at overclocking. We'll cover how to do it, what sort of performance you can achieve, problems and potential solutions, etc. Overclocking can be frustrating, rewarding, fun, and dangerous. We don't mean "burn the house down" dangerous, but you could certainly end up ruining some or all of your computer components. We take no responsibility for any difficulties or losses you may experience by using the information in this article, and we certainly take no responsibility for any damage that may occur to any person, place, or object. The manufacturers of the parts that we are using are also not accountable for any loss/damage that may occur - most companies void your warranty for overclocking. It's a risk, and it's your risk - proceed with caution. Finally, overclocking is never a "guaranteed result". You may or may not match the results that we achieve. We'll be happy to offer suggestions if you need them, as will many of our forum members. Patience and research are part of overclocking as well, so please understand that you may have to do some work on your own. If you can accept those warnings, we hope that you enjoy this article.
Back in the day, overclocking was in some ways simpler than what we see now. You would typically buy a mid-range processor and then try to increase the bus speeds as much as possible in order to get the most performance out of your system. Older Pentium chips also allowed you to change the multiplier, so with some luck, you might get your 2.5X multiplier on a Pentium 166 up to 3.0X, resulting in a 33 MHz overclock. Other than a few special chips like the Pentium M and Athlon FX, increasing multipliers is no longer possible. The modification of bus speeds can still be used, but it isn't necessarily the best or only way to try to overclock your system. We have mentioned overclocking performance in many articles, but we haven't taken the time to really explore all the options out there. We also know that current Intel and AMD setups have very different options and performance when overclocking is used, so we want to look at that as well.
Before we branch out into AMD vs. Intel comparisons, however, let's talk about the past top performers. The Celeron 300A is fondly remembered by many people, and with good reason. Yes, we have had some other good parts in the intervening years, like the 2.4 GHz Northwood cores, the low end Prescott cores, and the Athlon XP-M Barton parts. However, when you look at the 50% overclock of the Celeron 300A (and it wasn't just possible, it was common), none of the other parts have really ever approached that level of overclocking without some serious investment in cooling options. (Some people even managed to get the 300A to 504 MHz - an amazing 68% overclock!) Northwood's 2.4 GHz to 3.2 GHz is still an impressive 33% overclock. The 2.4 GHz to 3.6 GHz Prescott overclock (using the 2.4A) actually matches the 50% of the 300A, but you sacrifice some features (HyperThreading and high FSB speeds) with the lower model parts. Meanwhile, the overclocking darling that was the XP-M 2500+ "only" managed a typical overclock of 1.87 GHz to 2.4 GHz, a 29% overclock.
That brings us to the part that we're investigating today. It is arguably the best overclocking platform since the old Celeron 300A: AMD's Venice core. One thing that we didn't mention above is the role that price plays for many overclockers. Sure, the Athlon-FX can reach clock speeds and performance that most other chips only dream about, but at a cost of roughly $900 just for the processor, a lot of people will only read about it. What made the 300A so attractive was that it was not only a monster overclocking chip, but it cost around $150 and competed with $500 chips. That's why the 2.4C and 2.4A Pentium 4 are also well regarded; they cost under $200 and could compete with chips that cost two to three times as much. The price of entry for the cheapest Venice core (the 3000+) is once again very low; $120 for the OEM model, or $145 for the retail version.
We'll get into the details more in a moment, but for now, we'll just say that the 3200+ may actually be a better choice, and that's what we are using for this article. We are also using the retail model, and some people will say that retail parts tend to overclock better than the OEM chips. We'll simulate 3000+ overclocking using a 9X CPU multiplier, but that may or may not be an entirely accurate representation of 3000+ overclocking performance. In general, though, what we're hearing is that almost all of the Venice cores can run at very high clock speeds with a bit of effort, so there isn't a huge difference between 3000+ parts binned for 1.8 GHz and 3800+ parts binned for 2.4 GHz. AMD has simply set the package to use a maximum 9X multiplier on the former and a 12X multiplier on the latter. Talking about CPU multipliers leads us into the real meat of the discussion, though, so let's get into it.
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Crassus - Tuesday, October 4, 2005 - link
First of all, thank you for such a long article. I appreciate the work you put into this. What I'd really like to see in one of the planned articles would be an in-depth coverage of the options an enthusiast-grade mainboard BIOS offers nowadays for the RAM timings (and maybe PCIe) - beyond the standard timings covered in this article.PrinceGaz - Tuesday, October 4, 2005 - link
The finer memory-timings offered by enthusiast mobos are generally vendor specific so your best bet is to check a forum or other site dedicated to your motherboard. For DFI mobos for instance, you can find a thread which gives detailed coverage of memory settings on DFI-Street forums http://www.dfi-street.com/forum/showthread.php?t=2...">hereCheesePoofs - Tuesday, October 4, 2005 - link
Why stability test with 3dmark (an app that tries to stress teh CPU as little as possible) and pcmark (an ok pc-stressing app) instead of the combo of memtest86+, superpi, and prime95? Seems to me that if you want to find out whether yoru CPU really is stable, you'd want to stress it as hard as possible (which those three will do).Also, from what I've read from Zebo's thread in the CPU forums, 2T really doesn't have a significant impact on performance. Could you clarify this?
JarredWalton - Tuesday, October 4, 2005 - link
I've seen systems that run Prime95 and SuperPi 100% stable crash under 3DMark looping, as well as under PCMark. I imagine 2.80 GHz will crash under those if I run them all concurrently. My personal experience is that SuperPi and Prime95 only stress a few paths of the CPU, hence the inclusion of benchmarks with 11 different applications that can all fail with an unstable overclock. 3DMark GPU tests are not as demanding of the CPU, but the CPU tests are very demanding IMO. (That's part of why the top scores on the 3DMark ORB never include the CPU tests.)2T command rate, as you can see in quite a few instances, really killed performance. Perhaps tweaking other special timings beyond CL, tRCD, tRP, and tRAS might make the impact less, but you could likely tweak the same things with 1T at a lower memory speed. Command rate comes into play on every single memory access, so doubling that delay will certainly have an impact on performance.
fitten - Tuesday, October 4, 2005 - link
Good answer. Most have no clue as to how a CPU actually works. Ideally, a synchronous circuit is rated at a clock speed that the longest path will function properly (give correct results). There may be 1000s of pathways that can run at higher frequencies but that one can hold it back. Running the clock rate up may cause that one pathway not to be able to meet something like a data setup and hold time on one line (of the 32 or 64) in the data path and now you have an unstable setup that you may not detect. As always with overclocking, a crash is the best result you can get because you know you've pushed too far. Unless you are testing pretty much every instruction with every possible data against a control to compare against (some pathways can take longer depending on the data that it is being operated on), there are many errors that you may not detect... and all it takes is one, out of the possible billions, to make your machine not stable. Sure, it may be a rarely seen case of instruction+data but it exists.Programs like the Pi calculators and such do make your CPU work a lot, but the calculations are fairly repetitive and hardly a broad sample of the ISA.
I'm all for doing whatever you want with your own machine. Heck, I used to overclock all the time, too. I just find all of the lack of knowledge in synchronous circuits... interesting... when people talk about overclocking.
Saist - Monday, October 3, 2005 - link
for those who read this portion here :****
Because of the GPU limitation, we're going to be testing at 640x480, 800x600, and 1024x768. We'll also test many of the titles with 4xAA enabled, which should serve as a reality check. Even with a super fast CPU, many games are going to be completely GPU limited with the X800 Pro when we run 4xAA, especially at resolutions 1024x768 and above. Frankly, we wouldn't bother enabling 4xAA unless you can at least reach 1024x768 anyway.
****
Did anyone else think... okay.. lets stick a Radeon 9600, GeforceFX, or XGI Volari in there so that we actually will be limited? I mean... please. X800 alone goes above what most users have in their systems today. If we are buying "new" components, then yeah, the X800 is on my short list, but how about doing some reviews over hardware people actually have in their hands.
OvErHeAtInG - Tuesday, October 4, 2005 - link
If you're overclocking a new A64 Venice... somehow I think you're not still running your XGI Volari for games. Remember bench numbers are really only useful if they reflect framerates you would actually want to play with.JarredWalton - Tuesday, October 4, 2005 - link
The reason I used an X800 Pro is because I feel it's a good match for the chip, RAM, and motherboard. I can toss in a 7800GTX to show what the CPU on its own is capable of, but you can get cards that pretty much equal the X800 Pro for under $200. X800 GTO and GTO2 can match and even beat the X800 Pro.I view overclocking (and computer building in general) from a bang-for-the-buck perspective. It doesn't make sense to me to spend $100 upgrading from the 3000+ to the 3500+ if I'm going to be completely GPU limited. $200 on a graphics card is not that much money, when you really get down to it. 180 million transistor chip with 256MB of 980MHz RAM, all mounted on a large PCB? At least I can feel I'm getting a lot of stuff for $200. A CPU is far cheaper to produce (though more expensive to design). Profit margins on CPUs are notoriously high.... Personally, the X800 Pro is a decent card, but I really want something faster these days. Same goes for the 6800GT. But then, not everyone feels that way.
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Thought #2 (for Saist): If X800 is above what most people have, other than those buying new computers... well, what about the motherboard and processor? Socket 939 with nForce4 is a more recent configuration than X800/6800 cards. Not to mention Venice has only been out for something like 8 months.
If you're looking to spend $120+ on a new Venice chip and you've only got a 9600 Pro (or even a 9800 Pro), you're wasting your money on the wrong part (at least from a gaming perspective). A socket 754 Sempron with an X800 Pro would be far better for gaming than a Venice core with anything less than an X800/6800. Outside of gaming... well, graphics don't matter outside of gaming much, which is why Winstones, PCMark, and AutoGK are included.
Honestly, I'm not entirely sure if you were complaining about the use of a GPU that was too fast, or that it wasn't fast enough. For frequent gaming, I wouldn't recommend anyone go lower than about the X800 GTO these days. 6600GT is (IMO) now relegated to the budget/moderate-gaming setup, as many games are simply unplayable above 1024x768. I really don't like to drop below 1280x1024/1280x960 if I can avoid it. If I've misunderstood your complaint, let me know; if we simply have a difference of opinion... well, there's not much to do about that. :)
yanman - Tuesday, October 4, 2005 - link
any chance you can add in benches for 7800GT/GTX? after all, in your discussion you correctly asset that money is much better spent on high spec'd GPU to match the cpu speed that you've managed to overclock to - having used bargain rate ram and venice.i have a venice 3000+ clocked at 2686mhz, 7800gt and 2x1gb sticks of average ram (legend/hynix). until i upgraded the ram a few weeks ago i had it running for prehaps a month and a half totally solid with 2x512mb sticks of same type, at 2696mhz (337x8, ram at 225mhz (2:3) 2.5-3-4-7-1T)
the reason i ask for 7800GT and GTX is 2 fold, so we can see it from an nvidia side too (different cpu scaling maybe?), and also to show the scaling for a top-end card even if only as a reference point. It just seems a bit one-dimensional only using 1 card.
One last thing, well done to Zebo who made the excellent "Quick and dirty A64 overclocking guide" (used to be sticky in the forums) which I and many people I know used to overclock their venices with.. i'd be stuck without it!
JarredWalton - Tuesday, October 4, 2005 - link
I'm planning on doing 7800GTX testing with an X2 3800+ OC article. For gaming, it will perform identically to the 3200+ Venice. Hopefully, I'll be done in the next ~week or so.