I agree with you in the general case. I looked at the AMD and Intel specs to see that both use the CPUID instruction function 80000001H to set bit 11 in EDX if

I agree with you in the general case. I looked at the AMD and Intel specs to see that both use the CPUID instruction function 80000001H to set bit 11 in EDX if SYSRET is supported. Because both AMD and Intel 64-bit processors support the same general instruction set, software written to check only bit 11 could easily run into the scenario I described. Again, I do not know best practices in detecting CPU features, but I do know software developers often tend towards the least necessary to do the the job.