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mtbdudex

macrumors 68030
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Aug 28, 2007
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I've had my 2023 MBP M3 Max nearly a month now, 4TB SSD.
This morning plugged in my iPhone 14 Pro 1TB backing up, check iStats for process outta curiosity, saw 250.6% for photos, whats up with that?
How can processes be over 100% ?

Screenshot 2023-12-17 at 8.21.19 AM.png
M3 Max at 250%
 
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jdb8167

macrumors 601
Nov 17, 2008
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It's using 2 cores fully, and half of a 3rd.
I don’t know anything about iStats but I do see Activity Monitor showing 400% when it is using all four efficiency cores and none of the performance cores. So even then the percentage is misleading. It actually is using about 20% or less of the actual computing power of my M2.
 
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jdb8167

macrumors 601
Nov 17, 2008
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Hmm, so should iStats then smartly scale the processes to # cores so the math is never over 100%
It can get very complicated. Apple has a command line tool called powermetrics that shows performance to a much more accurate scale and there are third-party applications that can show this information as graphical data.

asitop

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mfram

Contributor
Jan 23, 2010
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Hmm, so should iStats then smartly scale the processes to # cores so the math is never over 100%

There is a UI standard for performance monitoring apps that "100%" means one core or thread of execution. So with multiple cores the total performance available is 100% times the number of core/threads. Programs written in a way that they can use multiple threads to increase performance can therefore use more than 100%.

Alternatively, you could "scale" the UI display like you said so that total performance is 100%. But if you do that, people will start complaining that single-threaded programs will "never go over 18%" on a machine with 6 processors.
 

ChrisA

macrumors G5
Jan 5, 2006
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Redondo Beach, California
I've had my 2023 MBP M3 Max nearly a month now, 4TB SSD.
This morning plugged in my iPhone 14 Pro 1TB backing up, check iStats for process outta curiosity, saw 250.6% for photos, whats up with that?
How can processes be over 100% ?

View attachment 2326020 M3 Max at 250%
What this display is telling you is that overall the computer is 77% idle. So it is mostly doing nothing.

Then giving more detail it says that the Photos App is using two and a half cores. The author of iStats chose to to use a scale where one core equals 100% under the processes header and a different scale (whole computer = 100%) under the CPU header.

There are other ways to display machine utilization, but this method works well enough. It is telling you that the computer is lightly loaded, mostly sitting idle with most of the RAM not in use.
 

Basic75

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May 17, 2011
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The author of iStats chose to to use a scale where one core equals 100% under the processes header and a different scale (whole computer = 100%) under the CPU header.
That's not the author of iStats, that's how Unix systems have shown the load on multi-processor machines for decades.
 
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Chancha

macrumors 68020
Mar 19, 2014
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In iStats settings, CPU & GPU, in the drop down “App usage format” you can go away from the default “Unix style (0-####%)” to “0-100%”.

The wordings in this drop down was enough for me to understand what it was doing, the first time I saw it years ago.
 
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