Arbitrary x86 codes arbitrary?

Question

Are x86 operating codes produced?

Is there a reason why it hltis 0xf4 and nop0x90?

Answer 1

Very early versions of this architecture (8008,8080) were implemented using an extremely small number of transistors / logic gates.

At that time, I am sure that the designers chose codes for operations and commands that were easily decoded (for example, the smallest number of gates). The instructions were simple and regular in format.

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