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x87 support may not be the most obscure part of the instruction set. Ther is also hardware support for BCD math in 16 bit amd 32 bit mode. Who uses that anymore?

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Unfortunately some exchanges (twse) uses packed BCD encoding.

BCD allows for insanely fast conversion to and from decimal string representation. And if doing arithmetic in it is only slightly worse than doing it in binary... it may actually be faster on the whole for some workloads.

But those instructions were dropped in 64 bit mode.

bcd is a reasonable way to do fixed-point decimal arithmetic.

binary floating point, let alone IEEE, is almost useless for implementing decimal arithmetic.

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