20120531, 14:48  #1 
May 2012
6_{16} Posts 
Maximum number of threads for Prime95
I am trying to test a 64 core system. I launched the 64 bit Prime95, of version 27.7, the latest. Prime95 crashes quickly. In the prime.txt file, located in the same folder of prime95.exe, I see only w0  w49, so I guess only 49 worker threads are up. But from the Prime95 wiki, it says for 64bit, the maximum worker threads are 64.
http://en.wikipedia.org/wiki/Prime95 What can I do to make it work? Thanks! 
20120531, 15:03  #2 
"Vincent"
Apr 2010
Over the rainbow
5·11·53 Posts 
Test: worker windows and adjust?
(just a nitpick 049 is 50, not 49) 
20120531, 18:31  #3 
Basketry That Evening!
"Bunslow the Bold"
Jun 2011
40<A<43 89<O<88
3×29×83 Posts 
I can't say off the top of my head, but I would say take a look through readme.txt, undoc.txt, and maybe even whatsnew.txt and do a Ctrl+F on some relevant terms.

20120531, 19:10  #4 
1976 Toyota Corona years forever!
"Wayne"
Nov 2006
Saskatchewan, Canada
5322_{10} Posts 
I have 64 bit V26.2.1 and according to my undoc.txt the limit in that version is 32 workers.
Worst case you could have 32 workers with 2 cores per worker and still probably get 95+% effectiveness. However post #2 in the Prime95 V27.7 thread implies it supports more than 36. http://www.mersenneforum.org/showthread.php?t=16779 Also read posts 31+. Last fiddled with by petrw1 on 20120531 at 19:15 
20120531, 19:57  #5 
May 2012
110_{2} Posts 

20120531, 20:04  #6  
May 2012
2×3 Posts 
Quote:
I tried version 27 on a 48 core system, and I got 100% of stress load of each every of the cores, then I tried to start 49, 50 or 64 threads, then Prime95 would crash. OK, I will try to launch 2 instances of prime95, with 32 threads each. 

20120531, 20:13  #7  
May 2012
6_{10} Posts 
Quote:
Forgot to say earlier, thank you for all your input! Attached please find the screen shot of the 48 core system. 

20120531, 20:17  #8  
May 2012
2×3 Posts 
Quote:


20120531, 22:40  #9 
P90 years forever!
Aug 2002
Yeehaw, FL
2^{6}·3·43 Posts 
Ship your 64core system to me and I'll do some debugging. I should have the system back to you in a year or two :)
Last fiddled with by Prime95 on 20120531 at 22:40 
20120531, 22:59  #10 
"Mr. Meeseeks"
Jan 2012
California, USA
37·59 Posts 

20120616, 01:15  #11 
Bemusing Prompter
"Danny"
Dec 2002
California
9C7_{16} Posts 
A scrollable MDI would be quite useful in this case: http://www.mersenneforum.org/showthread.php?t=16083

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