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From: John Savard <quadibloc@servername.invalid>
Newsgroups: comp.arch
Subject: Re: Stealing a Great Idea from the 6600
Date: Sat, 20 Apr 2024 18:01:49 -0600
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On Sat, 20 Apr 2024 01:06:33 -0600, John Savard
<quadibloc@servername.invalid> wrote:

>On Fri, 19 Apr 2024 18:40:45 +0000, mitchalsup@aol.com (MitchAlsup1)
>wrote:
>
>>So how does a 32-register thread "call" an 8 register thread ?? or vice
>>versa ??
>
>That sort of thing would be done by supervisor mode instructions,
>similar to the ones used to start additional threads on a given core,
>or start threads on a new core.
>
>Since the lightweight ISA has the benefit of having fewer registers
>allocated, it's not the same as, slay, a "thumb mode" which offers
>more compact code as its benefit. Instead, this is for use in classes
>of threads that are separate from ordinary code.
>
>I/O processing threads being one example of this.

Of course, though, there's nothing preventing using the lightweight
ISA as the basic for something that _could_ interoperate with the full
ISA. Keep all 32 registers in each bank, and have a sliding 8-register
window, or use bundles of instructions,  say up to seven instructions,
using one of three groups of eight integer registers and one of four
groups of floating-point registers. (The fourth group of integer
registers is the base registers.)

John Savard