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Old 2016-02-24, 18:47   #1
aweyhau
 
Feb 2016

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Default One slow worker process

Hi all -

I'm running Prime 95 on an iMac i7 (the computer is at work and I don't have the exact model number with me right now). I usually run four worker processes, usually double-checking small exponents. Within the last month or so, one of my worker processes has gotten very slow, going from about 14 ms per iteration to about 50 ms per iteration. The exponent size hasn't changed much, and the other workers are doing these exponents 4-5 times faster. (This same worker used to do the same speed as the others.) I suspect that it for some reason isn't "working as hard as it could" because my fans don't run as fast as they used to and because I'm only at 350% or so of CPU usage.

I'm not much of a hardware guy... any troubleshooting advice? I don't really have any idea about what's going.
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Old 2016-02-24, 23:10   #2
kladner
 
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You might well be seeing temp throttling. It is not easy to clean All in One cases and laptops. I have the impression that Apple products are very hard to get open. Try blowing out the intake and exhaust openings and see if the core comes back up to speed.

Another possibility is that some background program is stealing CPU cycles from Prime 95. This sort of thing can frequently hit on just one core. Is there a Mac utility that could show you the activity of each core in terms of what is using it? I have not dealt with Macs for years, so I may be totally off base in this.
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Old 2016-02-25, 00:46   #3
Prime95
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I was wondering if this could be an error in detecting hyperthreaded CPUs. Does Options/CPU indicate this is a hyperthreaded CPU?
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Old 2016-02-25, 03:28   #4
axn
 
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If this was due to hyperthreading, then the problem should affect a pair of workers. That can't be it.

If it was throttling, it would affect all workers. That can't be it either.

I would go with kladner's second suggestion of looking for other background programs stealing cycles.
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Old 2016-02-25, 04:14   #5
aweyhau
 
Feb 2016

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These are some great suggestions. I'll check my running processes and see if I see anything; if not, I'll post the list here and also give some more details about my chip tomorrow when I get in the office. (We had a snow day today, of all things.) Wouldn't hurt to see if I can blow some crud out of the fan slots so I'll try that too.

I did try quitting a couple of processes that I thought might be stealing (Quicksilver and the OneDrive Mac client) but neither of those changed anything. (That OneDrive client still seems heavy but quitting it made no change.)

I'll post more information tomorrow.
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Old 2016-02-27, 18:57   #6
aweyhau
 
Feb 2016

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We've all had those embarrassing, tail-between-the-legs moments when we know better but didn't do the obvious things... I'm afraid this is one of mine. When I got to work, the power had "blipped" and my computer was off. I started it up, and Prime95 is running great. Apparently this was some process stealing cycles. I had check "Activity Monitor" for this and didn't see anything, but I didn't think to try a restart. (head-slap)

Thanks for all the help! I'm back crunching away double checking...
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