mersenneforum.org  

Go Back   mersenneforum.org > Great Internet Mersenne Prime Search > Hardware

Reply
 
Thread Tools
Old 2006-10-18, 16:39   #1
WileECoyote
 
Sep 2006
Turlock, CA

5 Posts
Default Problems running Prime95 on a dual processor

I have been running Prime95 since 2000, but this is the first time I've run it on a dual core processor. I just built a new box with a AMD X2 4200+. When I ran one copy of Prime95 on CPU 0, the Task Manager showed the CPU usage capped at 50%, so I was sure it was running on just one processor.

Then I blew the drive away and put in a larger hard drive. After running two copies of Prime95 according to the instructions and using different affinities, the Task Manager says copies are running at more than 50% of the CPU. Sometimes it's 72%-23%. Moreover, when I look at the iteration times in the windows, it's .200. But when the computer is idle, the times go down to .037.. Before I blew the hard drive away, I noticed System Idle Processes was sucking a lot of CPU cycles. But I was running a new, clean XP installation both times. I hadn't installed anything except device drivers.

So Prime95 works at the expected speed, after the screen saver kicks in. But it runs much slower when I look at the window. It's like the refrigerator light! I'm really confused as to what's going on.

Can anyone shed a litle light on the situation?
WileECoyote is offline   Reply With Quote
Old 2006-10-19, 05:01   #2
JuanTutors
 
JuanTutors's Avatar
 
"Juan Tutors"
Mar 2004

13·43 Posts
Default

I don't have a good answer, and I hope someone does. What I do on my INTEL dual core is not bother with affinities. My copies both run at 50%, even at priority 1. The system idle process gets no time at all. I don't know if the AMD chips are different, though.

Hope that helps.
JuanTutors is offline   Reply With Quote
Old 2006-10-19, 07:05   #3
Cruelty
 
Cruelty's Avatar
 
May 2005

22×11×37 Posts
Default

If you have cool&quiet enabled in BIOS, then disable it. Moreover if you have installed special CPU driver from AMD's web-page then uninstall it.
BTW: Do you have some AV software running?
Cruelty is offline   Reply With Quote
Old 2006-10-19, 14:44   #4
Kosmaj
 
Kosmaj's Avatar
 
Nov 2003

2×1,811 Posts
Default

I don't have a dual core cpu but from my experience with dual cpu machines I can tell you this:
. Return affinities to default for both processes: check both cpu-0 and cpu-1
. Disable the sreen-saver or set it to "black". Screen-savers with a lot action use a lot of cpu cycles even if everything is perfectly set.
. Try testing with two instances of another, less demanding software, like NewPgen, LLR, or pfgw. Or two instances of Prime95 factoring.
. Be sure to have good air-flow inside the box and good cpu cooling.
As Cruelty said disable cool&quiet. You need hot&noisy.
Kosmaj is offline   Reply With Quote
Old 2006-10-19, 15:28   #5
WileECoyote
 
Sep 2006
Turlock, CA

5 Posts
Default

Cool and Quiet isn't a feature of my board, I went cheaper board and more expensive processor. I don't have any AV software running, and in fact the machine has never been hooked up to the internet. I installed the drivers that came with the board, but no AMD drivers. I do have the screen save set to black though.

Thanks for all your help, that gave me a possible reason:

I have been using my old PCI video card, but I have not installed the drivers. I'm just using the native resolution. I have not installed them because I plan to buy a new video card later, and don't want to go through the hassle of an unclean uninstall.

So, could not installed the proper video drivers be causing my problems?
WileECoyote is offline   Reply With Quote
Old 2006-10-19, 17:40   #6
S485122
 
S485122's Avatar
 
"Jacob"
Sep 2006
Brussels, Belgium

22·439 Posts
Default

I am running a dual core processor but from Intel and never experienced anything like what you describe. System Idle Process is never using CPU it is used to visualise the time the CPU has nothing to do.

So the question remains what is holding up the two instances of prime 95 when there is no screensaver ? You look at the iteration times and see them at .200 seconds. When Prime95 does not have a thing to display (because of the screensaver shutting down the video) the iteration times show a normal value of .037 seconds.

I think you are right and that it is the absence of a video driver that causes the problem...

I would not bother about the clutter caused by installing a new video driver for a new card, it is not much: a few files and registry entries. Just look at the clutter caused by ordinary programs :-)

So go ahead and install the right video driver.

Last fiddled with by S485122 on 2006-10-19 at 17:43
S485122 is online now   Reply With Quote
Old 2006-10-20, 16:55   #7
WileECoyote
 
Sep 2006
Turlock, CA

510 Posts
Default

I installed the latest nVidia drivers last night, and that makes the problem worse. Now when I have the Prime95 window open, the iterations take even longer. But once the blank screensaver kicks in, I get the expected performance.

Anyone have any other ideas? I am considering flashing the BIOS back to the start and starting all over again.
WileECoyote is offline   Reply With Quote
Old 2006-10-20, 19:21   #8
lycorn
 
lycorn's Avatar
 
"GIMFS"
Sep 2002
Oeiras, Portugal

2·5·151 Posts
Default

Quote:
Originally Posted by WileECoyote View Post
But once the blank screensaver kicks in, I get the expected performance.
Dumb as my question may sound:

If the blank screen saver has kicked in, blanking the display, where do you read the P95 iteration times???
lycorn is offline   Reply With Quote
Old 2006-10-20, 19:35   #9
S485122
 
S485122's Avatar
 
"Jacob"
Sep 2006
Brussels, Belgium

22·439 Posts
Default

When he desactivates the screen saver (by hitting a key, moving the mouse...) the timing of iterations performed when the screen saver was active are visible...

I do not have a clue about what causes this behaviour : slow except when the screen saver is active... Active desktop content perhaps ?

A task list wiht their CPU time could perhaps provide an answer...
S485122 is online now   Reply With Quote
Old 2006-10-20, 19:37   #10
WileECoyote
 
Sep 2006
Turlock, CA

58 Posts
Default

I let the computer run with the monitor off for a couple of hours. When I turn the monitor back on, I can see what the iteration times were for the last hour with the monitor off in the window.
WileECoyote is offline   Reply With Quote
Old 2006-10-21, 05:01   #11
WileECoyote
 
Sep 2006
Turlock, CA

5 Posts
Default

Here's the other funny thing: when I look at the Task Manager, all the other processes are listed as using 0% of the CPU.

I have some other ideas. Before I put in a larger hard drive, I removed the PCI RAID card and I moved the video card to another PCI slot before beginning a clean install on a blank drive. I don't suppose either of those things could explain my problems?
WileECoyote is offline   Reply With Quote
Reply

Thread Tools


Similar Threads
Thread Thread Starter Forum Replies Last Post
Dual Core and running the same test..? Unregistered Information & Answers 1 2008-03-01 15:02
Program Optimization for dual processor machines Altrus Software 4 2005-09-26 15:19
processor problems jebeagles Hardware 16 2004-09-19 12:51
Dual Processor Pentium 4 runs Slow! brodin Hardware 5 2004-04-28 23:12
Problem running prime-net on debian (woody) dual processor thedagit Software 3 2002-10-19 05:57

All times are UTC. The time now is 20:10.


Thu Dec 2 20:10:30 UTC 2021 up 132 days, 14:39, 0 users, load averages: 1.50, 1.51, 1.75

Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2021, Jelsoft Enterprises Ltd.

This forum has received and complied with 0 (zero) government requests for information.

Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation.
A copy of the license is included in the FAQ.