20090104, 04:52  #12  
Jul 2008
San Francisco, CA
C9_{16} Posts 
Quote:
Intel(R) Core(TM)2 Quad CPU Q6600 @ 2.40GHz CPU speed: 3005.39 MHz, 4 cores I know a benchmark run isn't the same as when a LL completes and reports back, but maybe there could be a way for it to keep track so that eventually we can examine the statistics on error rates. Maybe there could be a checkbox on prime95 or on primenet where people could indicate if their computer is OC'd (and maybe even by how much). I think this is very important for GIMPS in the long term. Even those that just want to win the next prize might be doing themselves a disservice by OCing, and I bet they would like to know. Last fiddled with by stars10250 on 20090104 at 04:57 

20090104, 05:13  #13 
"Mike"
Aug 2002
16454_{8} Posts 
We sure wish there was an option with PrimeNet to alternate regular LL tests with doublecheck tests. (Or some userselectable ratio.) We think we've asked for this option several times over the years. At least with this option you would know if you were turning in bad results a lot sooner.
How many hours of testing an overclock for stability can you spare before you lose time against a regular machine that started work right from the beginning? 
20090104, 15:18  #14  
Jul 2008
San Francisco, CA
C9_{16} Posts 
Quote:
In my case, I'm overclocking a Q6600. The nonOC'd iteration times for my particular exponents were 96 ms (for all 4 cores) and are now 61 ms (for all 4 cores) when OC'd. That's nearly a 45% performance difference for a cost difference of $14 for a better heatsink (newegg rebates made my motherboard and memory cost the same as components for a stock, nonOC'd, system). This is why I'm eager to know the statistics about error rates for OC'd systems. The performance gain vs cost for OC is simply too large to ignore. I won't answer your question with a specific number, but my 45% performance improvement would probably let me tinker with my system for a few years (assuming a computer life of 7 years?) before I'd lose out to the stock speed computer. This brings up another question. If one of your results get doublechecked and found to differ, does primenet let you know? Meaning, if one has a bad computer that is constantly turning in results that are later proved to be wrong, does primenet let you know you have a problem computer on your hands? I haven't been around long enough to know, but I suspect not. 

20090104, 21:18  #15  
"Mike"
Aug 2002
2^{2}·1,867 Posts 
Quote:
The new PrimeNet may be able to but we haven't looked into it. This is our old Team Prime Rib stats page. At the bottom it shows the bad results. http://www.teamprimerib.com/rr1/bin/...er.php?u=Xyzzy 

20090104, 22:55  #16 
Aug 2002
Termonfeckin, IE
2675_{10} Posts 
Yes you can with the new Primenet. You just need to customize your report. For example:
http://v5www.mersenne.org/report_LL/...B1=Get+LL+data Replace xxxxx with your userid. 
20090105, 01:38  #17 
Jul 2008
San Francisco, CA
3·67 Posts 
Ok, I think I understand. Based on that url, I have two verified test results and then a whole bunch that are unverified. The unverified have an empty column for "Error code (if any)," so I guess if I see anything show up in there I'll know my computer messed that one up. I can try to monitor this and compare OC'd to nonOC'd computers, as I have a few of each. It will take some time for those to get verified, but at least I can keep alert for any problems. Thanks much.
Last fiddled with by stars10250 on 20090105 at 01:40 
20090105, 11:48  #18 
Aug 2002
Termonfeckin, IE
5^{2}×107 Posts 
No the error code tells you if there is an error code generated during the run. But not all error codes are harmful. If you have an incorrect test there is a separate heading under unverified LLs called bad LLs or something like that.

20090106, 05:00  #19 
Oct 2008
n00bville
1011010101_{2} Posts 
You overclock mostly because you're games (applications, ...) have to be faster. That prime95 will work faster is a side effect.
I´m a fan of overclocking, BUT I think if a newbie wants to do that he/she has to be informed and extra cautious about it. Imho you have to be experienced in overclocking to avoid getting hardware errors. 
20090106, 10:55  #20 
Aug 2002
Termonfeckin, IE
5^{2}×107 Posts 
Perhaps there was no reason to overclock in the preCore2 era when you usually got 1015% if you were lucky. With Core2 however you can easily get 4050% without tinkering with any other settings. For a 40% speedup, a bad LL test or two a year is quite acceptable IMHO.

20090106, 18:35  #21  
"Richard B. Woods"
Aug 2002
Wisconsin USA
2^{2}·3·641 Posts 
Quote:
System A is standardclocked and does 10 LL tests in a year, all reliable. System B is 40% OCed and does 14 LL tests in a year but 2 of those have incorrect residues. System C, doing doublechecks, and system D, doing triplechecks, are standardclocked and do 10 reliable LL tests per year. Assume that only one exponent is assigned (firsttime or DC or TC, but not overlapping any other) at a time. With only system A performing firsttime tests, GIMPS gets 14 firsttime LLs in 1.4 years, then gets 14 DCs on those from system C the next 1.4 years. Result: 14 doublechecked exponents in 2.8 years. With only system B performing firsttime tests, GIMPS gets 14 firsttime LLs in one year, then gets 12 DCs with matching residues plus 2 DCs with nonmatching residues from system C in the next 1.4 years. Then it gets 2 TCs with matching (to DCs) residues from system D in the next 0.2 year. Result: 14 doublechecked exponents in 2.6 years. Another way of looking at system B's output is that it produces 12 correct results per year (which are DCed in 1.2 years) and provokes 2 more correct results by the combination of systems C and D in 0.2+0.2 year. Same result: 14 doublechecked exponents in 1.0+1.2+0.2+0.2 = 2.6 years. These numbers seem to show that system B is a net plus for GIMPS throughput. Any oversights? In order to slow GIMPS throughput to 14 exponents in 2.8 years in the second case, system B would have to err at the rate of 4 erroneous residues in 14 LL tests. 

20090106, 19:34  #22 
Aug 2002
Termonfeckin, IE
5163_{8} Posts 
I must add here that I only do doublechecks and last year I did about 120 tests. Two of those were bad. And two still unverified.

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