18 Aug
2001
18 Aug
'01
2:52 p.m.
Tony Duell skrev:
> All right, I've really never looked into an
architecture without an
> accumulator.
There aren't many microprocessors without an
accumulator. But things like
the PDP11 don't have one. I can add R1 to R3, or one memory location to
another, or... No restriction on one of the operands being in a special
registers.
I take it you're no big fan of load/store designs?
> >I am not going to name any particular chips,
but I think that should
> >explain why I prevfer the 6809 to the 6502, for example.
>
> Because it's got more registers?
> I think the 6809 (at a glance) seems to have a lot more special cases and
Eh? Yes, there are some special-cases on the 6809 (MUL,
for example). But
the 6502 has many more. Heck, on the 6502 you have to use the X register
for one kind of indrect and indexed addressing and the Y register for the
other form (on the 6809 you can do any addressing mode with X or Y (or
with U or S for that matter). On the 6809 you can transfer values between
any 2 registers of the same size. On the 6502 you can't even transfer
between X and Y without destroying the accumulator contents (IIRC).
I was specifically thinking of all the different registers and the way you
combine them. But I've not got enough experience to make any insightful
comparisons.
--
En ligne avec Thor 2.6a.
"If Linux were a beer, it would be shipped in open barrels so that anybody
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-- Unknown