Re: Instr()

Mike Williams wrote:
"dpb" <none@xxxxxxx> wrote in message news:f8vp3v$v19$1@xxxxxxxxxxx

Well, strictly speaking, "micro-code" is another level below
machine code (for hardware that supported it)...

Micro code is actually required when creating many modern processors (including most modern Intel and AMD processors as used in pcs), which are often designed so that they perform lots of individual actions in order to execute a single specific machine code instruction, enabling a single instruction to actually perform quite a lot of work. The opposite of this strategy was used in RISC (Reduced Instruction Set) processors, which I think Apple and some others favoured for a long time, and in which a single machine code instruction often equated to a single action in the processor. I've lost touch with hardware in the last twenty years or so, and things have probably changed a great deal since those "simple days", but that's the general position as I remember it.

Sorta'...there's a decent Wikipedia article.

The point was that "assembler" is the "normal" programmer level of getting to the machine to generate machine code, whereas microcode is (again "normally" for a suitable definition of normal) something only done at CPU design time or for _very_ specialized purposes. Most modern hardware doesn't have writable control store does it? I have to also admit I've not followed the X86 architecture and while I'm sure there is some microcode involved, is it actually accessible/modifiable once the chip is packaged?

My prime experience was w/ HP-1000 which was a writable control store machine and we very painstakingly built a microcode FFT routine for longer than inherently supported time series on one embedded in the old HP 5451C Fourier Analyzer. That effort alone was nearly a year in getting it completed although that wasn't full-time on that task only...

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