Re: "Mini" tags to reduce the number of op codes

On Sun, 7 Apr 2024 20:41:45 +0000, mitchalsup@aol.com (MitchAlsup1)
wrote:

How do you attach 32-bit or 64-bit constants to 28-bit instructions ??

Yes, that's a problem. Presumably, I would have to do without
immediates.

An option would be to reserve some 16-bit codes to indicate a block
consisting of one 28-bit instruction and seven 32-bit instructions,
but that means a third instruction set.

How do you switch from 64-bit to Byte to 32-bit to 16-bit in one
set of 256-bit instruction decodes ??

By using 36-bit instructions instead of 28-bit instructions.

In complicated if-then-else codes (and switches) I often see one inst-
ruction followed by a branch to a common point. Does your encoding deal
with these efficiently ?? That is:: what happens when you jump to the
middle of a block of 36-bit instructions ??

Well, when the computer fetches a 256-bit block of code, the first
four bits indicates whether it is composed of 36-bit instructions or
28-bit instructions. So the computer knows where the instructions are;
and thus a convention can be applied, such as addressing each 36-bit
instruction by the addresses of the first seven 32-bit positions in
the block.

In the case of 28-bit instructions, the first eight correspond to the
32-bit positions, the ninth corresponds to the last 16 bits of the
block.

John Savard