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When I try to run Prime95 on a HP T5710(CPU is Transmeta TM5700@800Mhz), it works fine as long as FFT is not larger than 32k, it will immediately crush if FFT size equal or larger than 48k (only prime95 crush, no BSOD or other bad things). Why?

With max FFT not larger than 32k, I can run at any other settings, as long as I want(tested 2 hours without error). Also the machine passed MEMtest86 perfectly. What does FFT mean?

Prime95 also says L2 cache unknown, but that shouldn't be the cause I think.

The OS is Windows XP SP3 Professional N, Prime95 version is 28.10.

Please don't ask me why I'm stress testing such a niche/ancient machine, I just like to do it, let's make this thread technical-only.

Sam
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  • Is it the latest version of Prime95? What version are you running? – Mokubai May 22 '17 at 15:14
  • Yes, latest, 28.10 – Sam May 22 '17 at 15:18
  • Entirely speculative here, but transmeta has a rather unusual architecture. I wonder if you're hitting some bug unique to that – Journeyman Geek May 23 '17 at 06:42
  • Yes I also guessed that, but how do FFT size affect the test, what the meaning of FFT size in prime95 anyway? – Sam May 23 '17 at 12:10
  • It sounds like the fft size directly affects the amount of memory needed, which wouldn't be surprising considering what [fft is](https://en.m.wikipedia.org/wiki/Fast_Fourier_transform). Basically by increasing the "size" you are increasing the number of frequency "bins" and as a result the number of data blocks needed to store the results of the fft transformation. How much memory does Prime95 appear to be using at various values of fft size? – Mokubai May 25 '17 at 06:28

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