CPUID
AMD社のCPUの拡張機能フラグをEDXとECXに格納する。 EDXのビット 0 から 9, 12 から 17, 23と 24は、AMDのCPUではEAX=1の場合のCPUIDの結果と重複し、IntelのCPUでは未使用である。IntelのCPUでもsyscall, nx, pdpe1gb, rdtscp, lm, lahf_lm, abm/lzcnt, 3dnowprefetchに対応しているものもある。
↑ On some older processors, executing CPUID with a leaf index (EAX) greater than 0 may leave EBX and ECX unmodified, keeping their old values. For this reason, it is recommended to zero out EBX and ECX before executing CPUID with a leaf index of 1.Processors noted to exhibit this behavior include Cyrix MII and IDT WinChip 2.
↑ On early AMD K5 (AuthenticAMD Family 5 Model 0) processors only, EDX bit 9 used to indicate support for PGE instead. This was moved to bit 13 from K5 Model 1 onwards.