[Info-vax] OT: IA-128 ???

[glen herrmannsfeldt]

JF Mezei <jfmezei.spamnot at vaxination.ca> wrote:
(snip) 
< Question is whether this will continue forever. There comes a time where
< there are enough bits to do the work effiecently.
 
< And remember that the more bits you have, the bigger the instructions
< are, which means the more memory you need and the more cache you need in
< the cpu because your code takes up more room.

That is why IBM used base-displacement addressing for S/360.
It allows for relatively small instructions and still a large
addressing space.  At the beginning, many S/360 models had
8K or 16K of core, though a 24 bit addressing space.  

VAX (closer to on topic) allows one to choose the size of
the displacement in its addressing mode as appropriate.

-- glen