According to Intel's documentation on AVX, the new instruction set can only be accessed in 64-bit mode due to using the new VEX prefix ( http://en.wikipedia.org/wiki/VEX_prefix ) unless the documentation is wrong or I misread it. You can download the documentation at http://software.intel.com/file/37205 and it says so on the first page. I've never used AVX so I don't really know for sure.
As for disabling AVX through the BIOS, Intel managed to do it as indicated in this article (read the section just above the Conclusion/Summary): http://software.intel.com/en-us/articles...-sonar-x1/
I assumed that it's possible to disable AVX in all mainboard BIOSes, but I guess it's only a feature which is available on Intel mainboards and BIOSes. That sucks. If other people with Sandy Bridge or Ivy Bridge CPUs can confirm the instability with r2552 in 64-bit, that would help. Oh, and I guess you have to be using Windows 7 SP1 64-bit for AVX support. legend80, are you currently using Windows 7 SP1 64-bit? I assume that plain Windows 7 64-bit without SP1 will not have this problem since it doesn't support AVX yet.
As for disabling AVX through the BIOS, Intel managed to do it as indicated in this article (read the section just above the Conclusion/Summary): http://software.intel.com/en-us/articles...-sonar-x1/
I assumed that it's possible to disable AVX in all mainboard BIOSes, but I guess it's only a feature which is available on Intel mainboards and BIOSes. That sucks. If other people with Sandy Bridge or Ivy Bridge CPUs can confirm the instability with r2552 in 64-bit, that would help. Oh, and I guess you have to be using Windows 7 SP1 64-bit for AVX support. legend80, are you currently using Windows 7 SP1 64-bit? I assume that plain Windows 7 64-bit without SP1 will not have this problem since it doesn't support AVX yet.