> Microcode is effectively just a program. Can't you just write the same program in Verilog or whatever? I think the answer is "yes" No. FPGAs are basically b

> Microcode is effectively just a program. Can't you just write the same program in Verilog or whatever? I think the answer is "yes" No. FPGAs are basically big fat lookup tables, some clever partitioning logic, and a boolean function. Inputs and outputs are (from the perspective of the "programmer") simultaneous, and if you want to do any state-keeping, it has to be done in response to some transition (such as a clock pin strobing). State like registers. So you want to implement program registers and make those inputs be address and data lines, decode the instruction, map it to the appropriate internal "registers", then write out the data back to memory (if any), you're talking two transitions (or four if you want to reuse the address/data likes for fetch and load). The speed/heat/power/price at which you can do that is (for the most part) a function of how big that lookup table is. If you can decode a single instruction in 4 steps instead of 1, you usually should because it means you can strobe 4x faster (or everything else will be cheaper, lower-power, cooler, etc). Microcoding is a technique to doing this, but it's also a choice because there are limits to how little-power you can get, or how cheap fabricating any amount of silicon is, or even how low-level you can be meaningfully thinking about solving business problems, otherwise we'd all be using massively-parallel SBNZ-computers that float in the air.