[userbinator]

In the case that the value you're switching on is a byte, and all 256 values are present in the case (very common for an 8-bit CPU emulator), a switch is a single instruction. You can't get faster/simpler than that.

[haldean]

Not to nitpick, but doesn't it need to be two instructions? You first do a relative jump by the value you're switching on, which takes you to another jump that jumps you to the actual code for that case. I can't think of a way to do it in just one instruction.

[haberman]

Just do an indirect branch, using a table of target pointers. If you had the opcode in eax, the single instruction would be something like:

    jmp  [lookupTable + eax]

[haldean]

Ah, good point. Thanks!