- Reverse-engineering the register codes for the 8086 processor’s microcode (righto.com)
Like most processors, the Intel 8086 (1978) provides registers that are faster than main memory. As well as the registers that are visible to the programmer, the 8086 has a handful of internal registers that are hidden from the user. Internally, the 8086 has a complicated scheme to select which register to use, with a combination of microcode and hardware. Registers are assigned a 5-bit identifying number, either from the machine instruction or from the microcode. In this blog post, I explain how this register system works.