Re: x86S Specification

On Mon, 21 Oct 2024 22:02:27 +0000, BGB wrote:

On 10/17/2024 4:34 PM, EricP wrote:
>
Pros:
   Technically makes sense for PCs as they are.
Cons:
   Looses some of the major aspects of what makes x86 unique;
   Doesn't really solve issues for x86-64's longer term survival.
>

x86's long term survival depends on things out of AMD's and Intel's
hands. It depends on high volume access to devices people will buy
new every year or every other year. A PC is not such a thing, while
a cell phone seems to be.

>
Absent changing to a more sensible encoding scheme and limiting or
removing condition-codes, x86-64 still has this major boat anchor. But,
these can't be changed without breaking backwards compatibility (at
least, assuming hardware that continues running x86-64 as the native
hardware ISA).

Condition codes were never "that hard" of a problem wither in
pipelining nor in operand routing.

>
Though, ironically, most "legacy x86" stuff could probably be served
acceptably with emulators.
>

Every try to emulate A24 ? Address bit 24--when we looked at it, it took
more gates to remove it and put a bit in CPUID so applications could "do
the right thing" than to simply leave the functionality there.

>
If it can't maintain a performance advantage (say, if ARM and RISC-V
catch up or exceed the performance possible on higher end x86 chips), it
is effectively done.
>

x86 performance advantage has ALWAYS been in the cubic amounts of cash
flow running through the FAB to pay the engineering team budgets.