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Old 2006-01-23, 05:30   #1
Bemusing Prompter
ixfd64's Avatar
Dec 2002

45538 Posts
Default Prime95 causes lag even at priority 1

I've noticed that Prime95 still causes lag even at the lowest priority. For example, one of my laptops usually takes only one minute to complete a basic virus scan. However, with Prime95 running, it often takes over an entire day.

This is one of the reasons my father says he hates Prime95 (what a noob)!

This problem seems to affect laptops more. (Prime95 used to lag the client for the online game RuneScape on this desktop, but not anymore. I think the problem was on RuneScape's side, though.)

Anyone got an idea on what to do?


Oh, and I'm using the latest version, 24.14, by the way.
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Old 2006-01-23, 06:19   #2
Fusion_power's Avatar
Aug 2003
Snicker, AL

7·137 Posts

The only time I've seen that problem is when the memory use was set improperly with prime95 and it was running a p-1 test or when the system memory was inadequate to support the two separate programs. What is your memory set at in Prime95? How much memory does the system have? What is your page mode memory setting (control panels:system:advanced:performance)

If the base memory is limited and a very large spreadsheet (90 megs or more) is opened in Excel and prime95 is running at the same time, there is a conflict that results in caching data to the disk such that Excel becomes almost unusable. I added memory to my computer which completely eliminated this.

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Old 2006-01-23, 19:37   #3
Ethan Hansen
Ethan Hansen's Avatar
Oct 2005

23×5 Posts

Does your laptop processor have hyperthreading capability? If so, Prime95 hogs half the CPU resources unless you have two or more higher priority processes running. Windows treats hypeerthreaded processors as being two separate devices. As such, Prime95 is allocated one full "CPU" even when you have another CPU-intensive task running. Needless to say, performance suffers.

George released an experimental version 24.15 (do a search of this forum for the link) that pauses for 30 seconds when other activity is detected. The detection algorithm is overly sensitive -- on the desktop machine I am using now, Prime95 is active less than 25% of the time -- but it does make running it on hyperthreaded machines workable.

If your laptop processor does not have hyperthreading capability, something else is going on. Does the virus scanner run at idle priority? Some such products run real time scanning at normal priority levels but drop background, full-system scan priority down. The extreme difference in scan times you report suggest this could be the culprit.
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Old 2006-01-23, 20:57   #4
P90 years forever!
Prime95's Avatar
Aug 2002
Yeehaw, FL

24·32·53 Posts

Some disk defragmenters (and maybe virus scanners?) restart whenever prime95 writes its save file. You could use the PauseWhileRunning option from undoc.txt.
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