[TUHS] Re: Clever code

["G. Branden Robinson" <g.branden.robinson@gmail.com>]

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At 2022-12-13T12:58:11-0500, Noel Chiappa wrote:
> ... registers used to have two aspects - one now gone (and maybe
> the second too). The first was that the _technology_ used to implement
> them (latches built out of tubes, then transistors) was faster than
> main memory - a distinction now mostly gone, especially since caches
> blur the speed distinction between today's main memory and registers.
> The second was that registers, being smaller in numbers, could be
> named with a few bits, allowing them to be named with a small share of
> the bits in an instruction. (This one still remains, although
> instructions are now so long it's probably less important.)

Maybe less important on x86, but the amount of space in the instruction
for encoding registers seems to me to have played a major role in the
design of the RV32I/E and C (compressed) extension instruction formats
of RISC-V.

https://riscv.org/wp-content/uploads/2017/05/riscv-spec-v2.2.pdf

Regards,
Branden

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