Re: Oops (Concertina II Going Around in Circles)

On Wed, 08 May 2024 21:17:00 -0600, John Savard
<quadibloc@servername.invalid> wrote:

And if that isn't enough, the last two header types let you switch to
38-bit words composed of two 19-bit halfwords. *That's* what I do to
add a bunch of extra 32-bit instructions to the ISA, if some new
feature is so important that I don't want the instructions that deal
with it to have to be 48 bits long at least.

I decided to plan ahead, and expand the opcode space even further by
adding another header type.

Now, one has access to three alternate instruction sets, but instead
of those being fixed, the first two can be chosen from a pool of
sixteen... and the third from a set of 128 different possibilities.

Also, I've noted that each of those alternate instruction sets, while
billed as sets of 32-bit instructions, can actually have opcode space
reserved for longer instructions, just as is done in the primary
instruction set.

John Savard