Here's my informal and possibly screwy understanding of why translating to microcode doesn't really slow things down: When you've got a bunch of tasks to do, br

Here's my informal and possibly screwy understanding of why translating to microcode doesn't really slow things down: When you've got a bunch of tasks to do, breaking the task-execution process into a pipeline of steps may potentially increase the latency (how long does it take to do a single task), because, well, you've now got to go through several steps do do that task. But (assuming your pipeline is designed well), it will also increase the throughput (how many tasks can you do in a fixed amount of time). In software, it's likely that latency is not going to be a problem as long as you can get more throughput (you probably don't care if the time between when the program hits your opcode and the CPU actually executes your instruction is 1 nanosecond later than it conceivably could be as long as the number of instructions executed per millisecond is greater). In any case, yes, you need to expose the same machine code interface, not just so people can write new software using the same code, but so that old code continues to work. It would be a nightmare if every few years there were incompatible changes to the instruction set.