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They did have special opcodes in x86 but dropped it in x64: https://en.m.wikipedia.org/wiki/Intel_BCD_opcode https://en.m.wikipedia.org/wiki/Intel_BCD_opcode

• userbinator 9y ago
  ...and more puzzlingly, those opcodes just became invalid, and weren't reused for something more useful in 64-bit mode. It reminds me of LAHF/SAHF and segmentation --- both features that AMD decided to remove initially for AMD64, but were forced to reintroduce after it was discovered that things like virtualisation needed them. Unfortunately, the same is unlikely to be true of the BCD instructions...