I must fall back on "I know very little about Intel architecture". They do have different modes, which are actually more involved than just addressing. I get the impression some of the older ones have been abandoned.
They have far less assembler code to worry about carrying forward. Regardless, I doubt they support backwards compatibility nearly as well as MVS and family. My point is that XA took away 7 bits that were used for various purposes. Taking all 8 wouldn't have been a lot more painful. sas On Wed, Nov 27, 2019 at 1:00 PM Tom Marchant < 000000a69b48f3bb-dmarc-requ...@listserv.uga.edu> wrote: > On Wed, 27 Nov 2019 12:47:44 -0500, Steve Smith wrote: > > >Notwithstanding all the expert opinions, from my point of view, XA would > >have better gone to 32-bit addressing from the get-go. I don't see the > >benefit of the amode being part of the address. Seems to me it's been a > >lot of unnecessary complication, and we might have had twice the address > >space until the advent of z/Arch. I know very little about Intel > >architecture, but when 32-bit processors came out, they had 32-bit > >addressing (at least logically). This is, of course, rather moot now. > > Do Intel processors support bimodal addressing? Do their designers > care about compatibility with existing code? > > -- > Tom Marchant > -- sas
