Unfortunately, you simply aren't correct - the blame here can't be placed with Microsoft. The bug occurs in 64-bit code, which is using the AMD64 instruction se

Unfortunately, you simply aren't correct - the blame here can't be placed with Microsoft. The bug occurs in 64-bit code, which is using the AMD64 instruction set. This instruction set is incompatible with the older 32-bit i386 instruction set, but shares many of its features. During the move to AMD64, AMD decided to remove many features of the old architecture (for example, removing many one-byte instructions that were taking up valuable opcode space). However, they decided not to touch the AH/BH/CH/DH register access modes - yet it was entirely in their power to do so because they were developing a new architecture with no existing code. So, if you're going to blame someone for this, blame AMD for wanting to keep too many legacy features in what was designed to be a brand new architecture. For examples of a 64-bit architecture that aren't simply extensions of the 32-bit versions, look at AArch64 (compared with the classic ARM instruction set), or Itanium (Intel's ultimately-unsuccessful attempt to build a brand-new 64-bit architecture cleanly broken from the legacy 32-bit set).