Intel sued NEC for making 8086 clones, claiming that NEC ripped off Intel's microcode. NEC claimed they wrote their own microcode. NEC's chip didn't have the secret SALC instruction and Intel lost the case.
See: [https://www.righto.com/2023/07/undocumented-8086-instructions.html Undocumented 8086 instructions, explained by the microcode]
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