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Questions and Answers : Macintosh : I7 Fans
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R M Wilson

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Message 56710 - Posted: 20 Aug 2017, 14:18:23 UTC

I was running WAH2 on my i5 mid 2010 iMac with 12 Gb RAM. Using 100% of the CPUs at 85% of the time gave me a relatively hot but quiet iMac. I have recently purchased a 2017 i7 iMac with 48Gb RAM and although the computer is quite cool to the touch the fan (s) are really giving it some welly. I have now reduced usage to 50% of CPUs and 50% of CPU time. Why, on a more advanced machine with greater specs is this happening. I have spoken with Apple support and they are at a loss and recommend taking the machine to the local Apple Genius Bar for testing which, of course I'm loath to do until I get a reply from your good selves.
I look forward to your reply,

Mike Wilson

Bangor, Co. Down, UK
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Profile Iain Inglis
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Message 56711 - Posted: 20 Aug 2017, 16:57:09 UTC

I prefer to adjust the "% of the CPUs" rather than "% of CPU time" as the latter might produce a rather variable CPU load. Adjusting the CPUs produces a constant but lower load. So for your 50%/50% case then 25% of the CPUs should produce the same work rate.
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Profile Dave Jackson
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Message 56712 - Posted: 21 Aug 2017, 6:05:30 UTC - in response to Message 56710.  

I don't know what the monitoring utility is on a Mac but I would check to see what temperature the CPU is running at to see if it is genuinely getting too hot or if the issue is just with the fans. I agree a new machine should be able to max out the cpu and not sound like a jet engine! (At some point I will change my ageing desktop to water cooling to reduce the noise levels when it gets as hot as it did in June when air temps around it were above 30C.
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Harri Liljeroos

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Message 56714 - Posted: 21 Aug 2017, 8:20:03 UTC

I have no experience of Apple products but I have seen on other commercial computers (like Lenovo) that their design specifications for new computers are more tight than before. Cooling systems are targeted to "normal" rather low intermittent loads instead of constant full speed. So the overhead has become much smaller and computers are less rugged than what they used to (special designs excluded).
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Message 56803 - Posted: 8 Sep 2017, 11:50:01 UTC - in response to Message 56710.  

I've had a similar problem when running SETI projects. No one could provide a reason why it ran hot
(over 165 F.) I ended up installing a fan control that I use when SETI cranks up the heat. Either Macs Fan Control or smcFanControl might help you out. You can check them out at MacUpdate. com
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Questions and Answers : Macintosh : I7 Fans