> [microcoding] is common in processors today and allows greater flexibility
Microprogramming was already widespread since the 1960s. The early microprocessors, such as MOS Technology’s 6502, too, used microcode (in its “hardwired” form).
Microprogramming was already widespread since the 1960s. The early microprocessors, such as MOS Technology’s 6502, too, used microcode (in its “hardwired” form).
“An alternate approach, used in many microprocessors, is to use PLAs or ROMs (instead of combinational logic) mainly for instruction decoding, and let a simple state machine (without much, or any, microcode) do most of the sequencing. The MOS Technology 6502 is an example of a microprocessor using a PLA for instruction decode and sequencing.”:
edit: I realize that in some trivial sense any combinational logic is tantamount to a compressed ROM, but I mean that even in a design sense this seems like it's not far off from a deduped array of microinstructions.
The distinction might be whether the instruction breaks up into a sequence of discrete internal operations. Implementing this as a hardwired state machine is an optimization.
And classic 5 stage RISCs like most MIPS don't typically have microcode.
I never ended up doing any low-level programming professionally though. The person I worked with that was the best at SQL, I heard hated his college course with FPGAs.