Crashes in Prime95 with Zen 2

[Evil Genius]

I've been running Prime95 for some 10 years. Recently I replaced my Ryzen 7 1700, which had been working flawlessly, with a brand new Ryzen 7 3700x, the rest being kept the same. Since then, every night around 6 am for some reason, Prime95 crashes with an access violation.


Hardware:


AMD Ryzen 7 3700x (stock settings)

Asrock X370 Killer SLI with BIOS 5.40 (latest)

4x Kingston 4 GB DDR4-2133 ECC (memtest approved, of course)


Software:


Prime95 v29.8 build 3


Fault addresses (relative to image base):


0x1bc4f03
0x1bc50b9
0x1bc4f03


Normally I'd suspect the hardware, but the fault addresses all occur in the same subroutine and twice on the same address. Also the memory has been tested well and is ECC protected. So I hope the author is willing to take a look.

[Prime95]

I suspect it is the automated benchmark crashing.

Try doing a thoughput benchmark on a 4096K FFT. Select "Benchmark all implementations...".

If it crashes post results.bench.txt. Then we'll get a Zen 1 user to do the same thing to see which FFT implementation is crashing.

[Evil Genius]

It didn't crash at all with a 4096K FFT, so I decided to test what I'm currently working on: 4800K FFTs, 4 cores, 4 workers. It crashed immediately, so results.bench.txt only contains topology information, I'm afraid. You still want it?

[Prime95]

No need.

Add "Autobench=0" to prime.txt while I investigate.

[Prime95]

On second thought, do send the output.

My code review turns up nothing suspicious. For grins, please try adding "CpuSupports3DNow=0" in local.txt. I don't think that will make a difference.

One other possibility is a bug in the hwloc library.

Debugging may require remote access to zen 2 machine. Preferably linux.

[Evil Genius]

AMD Ryzen 7 3700X 8-Core Processor             
CPU speed: 4165.85 MHz, 8 hyperthreaded cores
CPU features: 3DNow! Prefetch, SSE, SSE2, SSE4, AVX, AVX2, FMA
L1 cache size: 8x32 KB, L2 cache size: 8x512 KB, L3 cache size: 2x16 MB
L1 cache line size: 64 bytes, L2 cache line size: 64 bytes
Machine topology as determined by hwloc library:
 Machine#0 (total=11269920KB, Backend=Windows, hwlocVersion=2.0.3, ProcessName=prime95.exe)
  Package (total=11269920KB, CPUVendor=AuthenticAMD, CPUFamilyNumber=23, CPUModelNumber=113, CPUModel="AMD Ryzen 7 3700X 8-Core Processor             ", CPUStepping=0)
    L3 (size=16384KB, linesize=64, ways=16, Inclusive=0)
      L2 (size=512KB, linesize=64, ways=8, Inclusive=1)
        L1d (size=32KB, linesize=64, ways=8, Inclusive=0)
          Core (cpuset: 0x00000003)
            PU#0 (cpuset: 0x00000001)
            PU#1 (cpuset: 0x00000002)
      L2 (size=512KB, linesize=64, ways=8, Inclusive=1)
        L1d (size=32KB, linesize=64, ways=8, Inclusive=0)
          Core (cpuset: 0x0000000c)
            PU#2 (cpuset: 0x00000004)
            PU#3 (cpuset: 0x00000008)
      L2 (size=512KB, linesize=64, ways=8, Inclusive=1)
        L1d (size=32KB, linesize=64, ways=8, Inclusive=0)
          Core (cpuset: 0x00000030)
            PU#4 (cpuset: 0x00000010)
            PU#5 (cpuset: 0x00000020)
      L2 (size=512KB, linesize=64, ways=8, Inclusive=1)
        L1d (size=32KB, linesize=64, ways=8, Inclusive=0)
          Core (cpuset: 0x000000c0)
            PU#6 (cpuset: 0x00000040)
            PU#7 (cpuset: 0x00000080)
    L3 (size=16384KB, linesize=64, ways=16, Inclusive=0)
      L2 (size=512KB, linesize=64, ways=8, Inclusive=1)
        L1d (size=32KB, linesize=64, ways=8, Inclusive=0)
          Core (cpuset: 0x00000300)
            PU#8 (cpuset: 0x00000100)
            PU#9 (cpuset: 0x00000200)
      L2 (size=512KB, linesize=64, ways=8, Inclusive=1)
        L1d (size=32KB, linesize=64, ways=8, Inclusive=0)
          Core (cpuset: 0x00000c00)
            PU#10 (cpuset: 0x00000400)
            PU#11 (cpuset: 0x00000800)
      L2 (size=512KB, linesize=64, ways=8, Inclusive=1)
        L1d (size=32KB, linesize=64, ways=8, Inclusive=0)
          Core (cpuset: 0x00003000)
            PU#12 (cpuset: 0x00001000)
            PU#13 (cpuset: 0x00002000)
      L2 (size=512KB, linesize=64, ways=8, Inclusive=1)
        L1d (size=32KB, linesize=64, ways=8, Inclusive=0)
          Core (cpuset: 0x0000c000)
            PU#14 (cpuset: 0x00004000)
            PU#15 (cpuset: 0x00008000)
Prime95 64-bit version 29.8, RdtscTiming=1

[Evil Genius]

You most probably already know this, but Zen 2 has double the AVX bandwith compared to Zen 1, so it can process AVX 256-bit at full speed. My own FFT implementation benchmark (determining the order of 18782*(2^32-1)^4096+1) went from 2m19 to 1m49, a 27.5% speed increase.


Also, why is there no exception reporting with a full register dump in Prime95? That helps enormously with fault finding. I could send you some source if needed.

[Evil Genius]

"AutoBench=0" did the trick for now!

[Prime95]

Any other Zen 2 users out there? Do they crash too on a 4800K all implementations FFT?

[mackerel]

Bed time now, but if you don't get more reports before tomorrow I can try it too.

[mackerel]

A quick run before I go into work, it crashed repeatably.

Settings:
CPU 3700X
P95 29.8b5
Windows 10, 64 bit
min/max FFT: 4800k
Unselected "benchmark HT"
4 cores
4 workers
Happens with "benchmark all implementations" checked and unchecked!

Looking at the output window, it is starting to do a test and then crashes almost immediately. There's a second or so of running before it does so, and there's nothing in the output other than hwloc stuff. When crashing the application closes without any further notice. No errors displayed in Windows.

If I leave it on default of 8 cores, 1, 2, 8 workers, that runs normally. So it seems limited to 4 cores/4 worker setting.