1 Reply Latest reply on Oct 20, 2016 2:20 PM by ray_m

    DirectX 12 support on pre SSE4.2 CPUs


      On latest drivers, starting from 16.4.2 I'm noticed that all DX12 apps exit to desktop so I debugged one of apps an noticed this:


      (8b8.294): Illegal instruction - code c000001d (first chance)

      (8b8.294): Illegal instruction - code c000001d (!!! second chance !!!)

      *** WARNING: Unable to verify checksum for C:\WINDOWS\SYSTEM32\amdxc64.dll

      *** ERROR: Symbol file could not be found.  Defaulted to export symbols for C:\WINDOWS\SYSTEM32\amdxc64.dll -


      00007ffd`a2776f0e f30fb8436c      popcnt  eax,dword ptr [rbx+6Ch] ds:00000000`1cc002fc=00000001


      Instruction popcnt is SSE 4.2 instruction, so my question is: DX12 is supported on non-SSE 4.2 CPU or not ?

      NVIDIA drivers works fine on non-SSE 4.2 CPUs, they use only SSE2 instructions in DX12 driver, so why you (AMD) enforces SSE4.2 ? I think driver should not enforce instruction set that OS is not enforcing, and Windows 10 x64 requires only SSE2 + CMPXCHG16B + LAHF/SAHF + PrefetchW.