Re: What is an N-bit machine?

On Thu, 28 Nov 2024 17:56:23 +0000, Thomas Koenig wrote:

On 2024-11-28, John Dallman <jgd@cix.co.uk> wrote:

In early computer designs, arithmetic registers were much longer than
addresses, the classic examples being machines with 36-bit words and 15-
to 18-bit addresses.
>
Large logical address spaces started with the IBM 360, which had 32-bit
arithmetic registers and 32-bit address registers. You couldn't put
32-bits worth of physical memory in a machine for over a decade after it
appeared, but it was allowed for in the architecture.

>
The original /360 had a 24-bit address space. The plan had been
to make it 32-bit clean, but some people didn't get the memo, reasulting
in a lot of hassle later on.

BAL -> BAS , ...
And assembly people using the upper 8-bits of base registers for
"interesting" things.