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If the 8086 uses microcode to implement its ISA using simpler operations, could a CPU that does away with the translation layer theoretically be made & if so wh
by ido 6y ago
If the 8086 uses microcode to implement its ISA using simpler operations, could a CPU that does away with the translation layer theoretically be made & if so what would the simpler underlying language or microcode look like?
What portion of the chip handled the translation?
- kens 6y agoThe 8086 uses "traditional" microcode, where microcode is executed to implement the instruction. Modern x86 processors are a bit different, translating an instruction into micro-ops which go into the instruction pipeline. So the 8086 may not be translating in the way you're thinking. In any case, look elsewhere in these comments for a discussion of the NEC V33 processor, which replaced the 8086's microcode with hardwired control. As for the 8086's microcode, each micro-instruction is 21 bits: 5 bits for a source register, 5 bits for a destination register, 3 bits for a "type" field, 7 bits for two more fields, and 1 bit to control the flags. The microcode ROM is the big rectangle in the lower-right of the die photos.