20110106, 15:27  #1 
Sep 2010
Scandinavia
615_{10} Posts 
Tweaking RAM & CPU
Hello,
I'm trying to figure out clock speeds, timings and voltages for my RAM, MB & CPU. Hardware: ASUS P7H55 i3 540 3.07 > 3.20GHz 4*2GB Corsair XMS3 1600MHz CL9 CPU & MB: I'm running the CPU at 160*20 instead of spec 133*23. Vcore is set to Auto, which amounts to 1.13~1.14V in practice. This seems to require ~53W at boot. But then runs at ~50.1W. I recently installed an additional fan, since then the core temp hasn't passed 58°C. Before that it would reach at least 61°C. Now; Should I tinker with core voltage, PCH voltage, IMC voltage or PLL voltage? Does the above make sense? Any comments, questions or tips? RAM: Spec says 99924 @ 1600MHz, 1.65V. I'm currently trying 89923 @ 160*10. Due to the rel. high voltage req. of these modules I have set IMC voltage to 1.15. Does anyone have any experience with this kind of modules? Softer stuff: I mostly use this computer for number crunching, so that should be kept in mind. Which of the above parameters should have the most impact on ECM & P1 performance? You might say I'm tuning this machine mainly for those two tasks. Where is(/are) the bottleneck(s)? Is there a simple way of knowing how much memory a specific ECM/P1 task will require to run optimally? More specifically I'm wondering what the relationship between bounds and number looks like when I'm willing to use say 6GB for a calculation. GPU?: Does it make sense to buy a GPU for the sole purpose of factoring? If so; what's the minimum $$$ for that to make sense? I have no idea how one would go about using a GPU for factoring. I've heard of GTX 470... Any other recommendations? Any feedback would be appreciated. 
20110106, 22:38  #2  
Account Deleted
"Tim Sorbera"
Aug 2006
San Antonio, TX USA
17×251 Posts 
Quote:
Code:
4) Factor in the information below about minimum, reasonable, and desirable memory amounts for some sample exponents. If you choose a value below the minimum, that is OK. The program will simply skip stage 2 of P1 factoring. Exponent Minimum Reasonable Desirable     20000000 40MB 80MB 120MB 33000000 65MB 125MB 185MB 50000000 85MB 170MB 250MB ECM memory requirements are probably similar given identical bounds and exponent. The "optimal" would probably be that the whole stage 2 can be done in one go, but more realistically, if you allow a few hundred MB it should be good. For ECM/P1, not at the moment, because AFAIK there aren't any ECM/P1 apps made for GPUs yet. They can do other sorts of factoring extremely well compared to modern CPUs though, (AFAIK roughly 10x100x faster, depending on how good of a GPU and what sort of factoring) and are at least on par with four modern cores on LL tests. The GTX 460 is another good suggestion. 

20110106, 22:41  #3  
"Oliver"
Mar 2005
Germany
11×101 Posts 
Hello,
Quote:
The primenet isn't limited by trial factoring at all so it doesn't make much sense. You'll need 2 of your CPU cores to feed the a GTX 470 if you're using mfaktc so you won't be able to run any LLs on CPU. So save your money. Oliver 

20110106, 23:19  #4 
Bemusing Prompter
"Danny"
Dec 2002
California
4510_{8} Posts 
I think Kleinjung (or was it one of his students) ported GMPECM to the PS3. However, the code isn't publicly available, so you might want to ask him about it.

20110107, 09:16  #5  
Sep 2010
Scandinavia
3·5·41 Posts 
Quote:
I'm hoping to find an approximation giving memory needed as a function of [FFT size or exponent] and bounds. About ~3.5hrs ago I finished a successful P1 run on M17873291. I did all 480 relative primes (that obv. weren't all relative primes, if my understanding is correct) in one run. It took ~4GB. I've noticed that the memory use in ECM is much more complex than that in P1. I would like to know the relationship in the case of ECM to. From what I've heard TF using GPU('s) is a reality. I'd be interested in that. Not solely for the purpose of GIMPS, but for the purpose of TF. I don't know what hardware and software it takes though... Any comments on the rest of my post? Hardware stuff? Come on people! This is the 'Hardware' forum! Thanks MiniGeek. 

20110107, 09:20  #6  
Sep 2010
Scandinavia
3×5×41 Posts 
Quote:
You mean that GIMPS is limited by P1 rather than by TF? That's my understanding. I'd be interested in faster TF anyway. For both GIMPS and other stuff. I've heard of mfaktc, never used it. How do you mean feed the GTX? Could you explain? Thanks! 

20110107, 12:26  #7 
"Oliver"
Mar 2005
Germany
10001010111_{2} Posts 
Hi!
In mfaktc the CPU does the preselection of factor candidates (sieving), a single core of the CPU you've mentioned can't generate these lists of factor candidates fast enough to keep a GTX 470 (in your example) busy all the time. Oliver 
20110107, 13:04  #8  
Sep 2010
Scandinavia
267_{16} Posts 
Quote:
Say you want to find the smallest factor of a given number. Should you use a i3 540 or a GTX 470? The latter would be faster, right? 

20110107, 16:00  #9 
"Oliver"
Mar 2005
Germany
11·101 Posts 
Take a look on that page: http://mersenne.org/various/math.php
When talking about mfaktc, the algorithm on that page is running on the GPU while the preselection of candidates (that part which mentions "sieve of Eratosthenes") runs on the CPU. 
20110107, 16:14  #10  
Jun 2003
7×167 Posts 
Quote:
Quote:
Bear in mind that the per pass overhead is small compared to the overall running time of the algorithm. If you double the number of relative primes per pass, from 20 to 40 say, you'll save X amount of time. Double it again, to 80, and the additional saving is X/2. The returns really do diminish quite rapidly. For this reason, when specing out a machine for GIMPS it's generally not cost effective to load it with vast amounts of memory. You'd do better to spend the money on a faster processor, faster memory, etc. I'm not familiar with how prime95 ECM uses memory, but I would imagine that the same principles apply. 

20110107, 16:43  #11  
Account Deleted
"Tim Sorbera"
Aug 2006
San Antonio, TX USA
17·251 Posts 
Quote:
Last fiddled with by MiniGeek on 20110107 at 16:47 

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