Summary of what instructions are implemented/unimplemented, as organized in the Instruction Set Summary of the Intel Software Developer Manual (volume 1 chapter 5).
Note: this summary is based on the opcode maps (see implemented-opcodes and subtopics). To the extent that the opcode maps are incomplete (as noted in several of the below topics), the instruction counts listed below and in subtopics are as well.
Total instructions: 3266, Implemented: 700, Unimplemented: 2566