Why large fft test given so much stress to cpu?

jiangv · 2020-05-08, 06:12

recently I use latest version of mprime 95 to test my mem kits, I found that if I choose large fft(test mem controller and ram), the core temp could went up to 80 degrees, almost the same as I use small fft(L1-L3, max temp) to stress cpu only.

so why it would be some much stress given to cpu when I stressing mem?

ewmayer · 2020-05-09, 19:42

Really good FFT implementations will stress both the CPU and the entire memory subsystem.

If your CPU has more than 4 physical cores you may well see less CPU stress for big-FFT since the memory typically can't keep up with the data demands of all the cores, but I'll defer to the owners of such systems to confirm or deny that.

jiangv · 2020-05-11, 13:07

Quote:

Originally Posted by ewmayer

Really good FFT implementations will stress both the CPU and the entire memory subsystem.

If your CPU has more than 4 physical cores you may well see less CPU stress for big-FFT since the memory typically can't keep up with the data demands of all the cores, but I'll defer to the owners of such systems to confirm or deny that.

Thanks, my pc has 18 cores and I do see temps at normal reading about 60-70 degrees, But still dont understand why large fft will cause such stress as much as small fft

2020-05-08, 06:12	#1
jiangv Jul 2019 3·5 Posts	Why large fft test given so much stress to cpu? recently I use latest version of mprime 95 to test my mem kits, I found that if I choose large fft(test mem controller and ram), the core temp could went up to 80 degrees, almost the same as I use small fft(L1-L3, max temp) to stress cpu only. so why it would be some much stress given to cpu when I stressing mem? Last fiddled with by jiangv on 2020-05-08 at 06:25

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2020-05-09, 19:42	#2
ewmayer ∂²ω=0 Sep 2002 República de California 2²·2,939 Posts	Really good FFT implementations will stress both the CPU and the entire memory subsystem. If your CPU has more than 4 physical cores you may well see less CPU stress for big-FFT since the memory typically can't keep up with the data demands of all the cores, but I'll defer to the owners of such systems to confirm or deny that.