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I was making a small x86 assembler once and I was frustrated that the encoding seemed almost random and very hard to generate. Until I fell over a comment in so
by kristiandupont 13y ago
I was making a small x86 assembler once and I was frustrated that the encoding seemed almost random and very hard to generate. Until I fell over a comment in some google group stating that the key to understanding it is that all opcodes are coded in octal. It's inherited all the way back from the 8080, but for some reason this information was nowhere to be found, including the official references from Intel that I had.
- Scaevolus 13y agoHere's an analysis of x86 encoding in octal: http://reocities.com/SiliconValley/heights/7052/opcode.txt http://reocities.com/SiliconValley/heights/7052/opcode.txt The author claims to know most 8086 instructions by memory alone!
- kristiandupont 13y agoWell, that was the exact post I used back in the day :-) It helped me a lot, it's a really good reference.