Investigations into Socket 939 Athlon 64 Overclocking
by Jarred Walton on October 3, 2005 4:35 PM EST- Posted in
- CPUs
Memory Options
Memory has been a major part of overclocking since we shifted to locked CPU multipliers back in the Athlon/Pentium III era. With the move to DDR RAM on the Athlon and Pentium 4, it has become even more important. Since all processors other than the Athlon FX chips (and Pentium M) are multiplier locked - at least on the high end of the scale - increasing your CPU clock speed means that you have to increase the system/CPU bus speed. If your default bus speed is 200 MHz and you have a 10X multiplier, you end up with a 2000 MHz processor. Raising the bus speed to 220 MHz would give you a 2200 MHz CPU, but it would also require memory that could run at DDR440 speeds. That's the way it normally works, and so we have unofficial memory speeds of up to PC4400 (DDR550) that allow you to overclock your bus, CPU, and RAM beyond the standard specification.
However, there are alternative methods of overclocking that may not require ultra high speed RAM. High speed RAM generally costs quite a bit more, and if your goal in overclocking is to get higher performance without spending a lot more money, doubling the cost of RAM defeats that purpose. We'll be looking at the impact of using the lower memory ratios in order to keep standard PC3200 at or below DDR400 MHz speeds. This means that you could use any PC3200 memory. There will be some performance loss, but the question is: how much? That's what benchmarks are for...
On the other end of the RAM spectrum, we find the high performance and high cost parts. Yes, you can buy some untested DIMMs with similar ratings to the high performance RAM for less money, but we're more interested in exploring guaranteed RAM speeds in this article, so we won't be taking that route. However, even if you can't reach the RAM speed that you want, our value RAM will serve as a minimum performance metric. At the high end, there are a few major contenders.
First, there's the high performance, high voltage RAM like OCZ VX and Mushkin Redline. (They probably use Winbond CH5 blanks, and we'll just use CH5 to refer to this memory from here on out. We could be wrong on the actual chips used, however.) You'll need a motherboard that can supply up to 3.5V to the RAM to get the most out of such memory, with 2-2-2-6 1T timings possible for as high as DDR533, give or take. You'll also want to get active cooling on the memory if you go this route. The next option is to grab some of the re-released Winbond BH5 DIMMs, which are similar to CH5 in that high voltages allow for 2-2-2-7 1T timings up to DDR500 speeds. The price and performance of these two options are roughly equivalent, with the CH5 generally reaching somewhat higher speeds. The drawback of CH5 is that it also requires at least 3.0V just to run at 2-2-2 timings and DDR400 speeds, where BH5 can do the same with only 2.6V. The final option is to go for the tried-and-true Samsung TCCD (or TCC5) DIMMs. You'll sacrifice some performance and have to lower the timings as RAM speeds increase, but the good news is that you won't need more than 2.80 to 2.90V to reach maximum clock speeds. You can also get TCCD DIMMs up to DDR600 and even beyond, which serves to counterbalance the better timings of BH5/CH5. The cost of Samsung TCCD is roughly the same as the other two choices.
So, which RAM do you choose? There are several factors, and in order to keep the number of benchmarks from rapidly bloating, we only used one type of value RAM and one of the performance RAM options.
For our high end RAM, we used what we already had available: OCZ Rev. 2 Platinum (TCCD memory as opposed to the newer TCC5 memory). One of the benefits of this RAM is that it doesn't run as hot as the BH5 and CH5 when overclocked, so active cooling won't be required at maximum clock speeds. Active cooling means more noise from your PC, and while few overclocked systems are truly quiet (without resorting to water cooling), many people will agree that adding more fans to the case isn't really desirable. This doesn't mean that BH5 or CH5 is a bad choice, and in many instances, either would be slightly faster than TCCx RAM.
The final pieces of the overclocking puzzle are the choice of case and power supply. Case selection influences (to a large degree) the number and arrangement of fans that you can use for cooling, though anyone with a bit of skill and a Dremel tool can add extra fans if needed. We'll talk a bit about heat sinks and fans for CPU cooling as well. First, let's start with the power supply, as it is more directly comparable to the components that we've covered so far.
Memory has been a major part of overclocking since we shifted to locked CPU multipliers back in the Athlon/Pentium III era. With the move to DDR RAM on the Athlon and Pentium 4, it has become even more important. Since all processors other than the Athlon FX chips (and Pentium M) are multiplier locked - at least on the high end of the scale - increasing your CPU clock speed means that you have to increase the system/CPU bus speed. If your default bus speed is 200 MHz and you have a 10X multiplier, you end up with a 2000 MHz processor. Raising the bus speed to 220 MHz would give you a 2200 MHz CPU, but it would also require memory that could run at DDR440 speeds. That's the way it normally works, and so we have unofficial memory speeds of up to PC4400 (DDR550) that allow you to overclock your bus, CPU, and RAM beyond the standard specification.
However, there are alternative methods of overclocking that may not require ultra high speed RAM. High speed RAM generally costs quite a bit more, and if your goal in overclocking is to get higher performance without spending a lot more money, doubling the cost of RAM defeats that purpose. We'll be looking at the impact of using the lower memory ratios in order to keep standard PC3200 at or below DDR400 MHz speeds. This means that you could use any PC3200 memory. There will be some performance loss, but the question is: how much? That's what benchmarks are for...
On the other end of the RAM spectrum, we find the high performance and high cost parts. Yes, you can buy some untested DIMMs with similar ratings to the high performance RAM for less money, but we're more interested in exploring guaranteed RAM speeds in this article, so we won't be taking that route. However, even if you can't reach the RAM speed that you want, our value RAM will serve as a minimum performance metric. At the high end, there are a few major contenders.
First, there's the high performance, high voltage RAM like OCZ VX and Mushkin Redline. (They probably use Winbond CH5 blanks, and we'll just use CH5 to refer to this memory from here on out. We could be wrong on the actual chips used, however.) You'll need a motherboard that can supply up to 3.5V to the RAM to get the most out of such memory, with 2-2-2-6 1T timings possible for as high as DDR533, give or take. You'll also want to get active cooling on the memory if you go this route. The next option is to grab some of the re-released Winbond BH5 DIMMs, which are similar to CH5 in that high voltages allow for 2-2-2-7 1T timings up to DDR500 speeds. The price and performance of these two options are roughly equivalent, with the CH5 generally reaching somewhat higher speeds. The drawback of CH5 is that it also requires at least 3.0V just to run at 2-2-2 timings and DDR400 speeds, where BH5 can do the same with only 2.6V. The final option is to go for the tried-and-true Samsung TCCD (or TCC5) DIMMs. You'll sacrifice some performance and have to lower the timings as RAM speeds increase, but the good news is that you won't need more than 2.80 to 2.90V to reach maximum clock speeds. You can also get TCCD DIMMs up to DDR600 and even beyond, which serves to counterbalance the better timings of BH5/CH5. The cost of Samsung TCCD is roughly the same as the other two choices.
So, which RAM do you choose? There are several factors, and in order to keep the number of benchmarks from rapidly bloating, we only used one type of value RAM and one of the performance RAM options.
Clck to enlarge.
For our high end RAM, we used what we already had available: OCZ Rev. 2 Platinum (TCCD memory as opposed to the newer TCC5 memory). One of the benefits of this RAM is that it doesn't run as hot as the BH5 and CH5 when overclocked, so active cooling won't be required at maximum clock speeds. Active cooling means more noise from your PC, and while few overclocked systems are truly quiet (without resorting to water cooling), many people will agree that adding more fans to the case isn't really desirable. This doesn't mean that BH5 or CH5 is a bad choice, and in many instances, either would be slightly faster than TCCx RAM.
The final pieces of the overclocking puzzle are the choice of case and power supply. Case selection influences (to a large degree) the number and arrangement of fans that you can use for cooling, though anyone with a bit of skill and a Dremel tool can add extra fans if needed. We'll talk a bit about heat sinks and fans for CPU cooling as well. First, let's start with the power supply, as it is more directly comparable to the components that we've covered so far.
Facebook
Twitter
RSS
101 Comments
View All Comments
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.
---------
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.