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Groups > alt.sys.pdp10 > #9952
| From | jayjwa <jayjwa@atr2.ath.cx.invalid> |
|---|---|
| Newsgroups | alt.sys.pdp10 |
| Subject | Re: Accumulator naming |
| Date | 2026-07-30 11:24 -0400 |
| Organization | atr2net 2026 |
| Message-ID | <87zez8pkku.fsf@atr2.ath.cx> (permalink) |
| References | <87wlulwflh.fsf@atr2.ath.cx> <mdd33x9cbvq.fsf@panix5.panix.com> <87se579i01.fsf@atr2.ath.cx> <mddqzklxxa5.fsf_-_@panix5.panix.com> |
Rich Alderson <news@alderson.users.panix.com> writes:
> Why shouldn't they then be referred to by numeric addresses just like
> the rest of memory?
It's confusing to new students and looks weird. Consider:
PRINT (MESS)
move 1, save ; Setting up RDTTY%
movei 2, 10 ; for 8 chars
setz 3, ; No reprompter ctrl-r
rdtty%
2,10? There's integers on both sides of the comma. And the SETZ
instruction looks like someone forgot to type part of the
line. Probably, if you've looked at it for 30+ years it makes sense, and
I am getting used to it by now, but it's the only CPU architecture I
could find going forward that does this.
https://en.wikipedia.org/wiki/PDP-11_architecture (PDP-11)
https://cybersandeep.gitbook.io/arm64basicguide/chapter-2-understanding-arm64-registers (ARM64)
https://www.ece.lsu.edu/ee4720/doc/vax-11780-arch-handbook.pdf (VAX)
(page 3-4 in the PDF itself, not your reader)
https://math.hws.edu/eck/cs220/f22/registers.html (x86-64)
https://en.wikipedia.org/wiki/MOS_Technology_6502#Registers (6502)
https://en.wikibooks.org/wiki/68000_Assembly/Registers (68000)
It's easier, at least for me, to make a "mental map" of where things are
when they have names rather than numbers, even if those names are
short. It's easier to recall "watermellon", "apple", "grape" than 39,
23, 5 even though both sets are decending in magnitude. We can assign
names, but see my next reply...
> Secondly, unlike the named registers in the X86/X64 architecture,
> there are no special case uses in the hardware for any accumulator.
I'm not sure if this is bad or good, but it's a bit like driving in the
city with no road markings. I've been using STDAC. since I found out
about it, and its mere presence indicates there was a need for it, but
people often do as follows (code from an ITS program):
A=1
B=2
T=10
TT=11
Q=16
P=17
...
LITES0: MOVE Q,PC
POP P,A
JSP Q,(Q) ;Coroutine call.
MOVEM Q,PC
DATAO PI,A ;Display A on memory indicators.
SOS TICK
POPJ P,
That is, assign accums as they see fit.
--
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Fizz Buzz jayjwa <jayjwa@atr2.ath.cx.invalid> - 2026-07-23 17:39 -0400
Re: Fizz Buzz Rich Alderson <news@alderson.users.panix.com> - 2026-07-23 23:19 -0400
Re: Fizz Buzz jayjwa <jayjwa@atr2.ath.cx.invalid> - 2026-07-25 12:00 -0400
Re: Fizz Buzz Rich Alderson <news@alderson.users.panix.com> - 2026-07-25 18:05 -0400
Re: Fizz Buzz jayjwa <jayjwa@atr2.ath.cx.invalid> - 2026-07-26 11:12 -0400
Accumulator naming Rich Alderson <news@alderson.users.panix.com> - 2026-07-29 18:10 -0400
Re: Accumulator naming scott@slp53.sl.home (Scott Lurndal) - 2026-07-30 15:14 +0000
Re: old architectures, was Accumulator naming John Levine <johnl@taugh.com> - 2026-07-30 20:40 +0000
Re: Accumulator naming Rich Alderson <news@alderson.users.panix.com> - 2026-07-30 18:41 -0400
Re: Accumulator naming jayjwa <jayjwa@atr2.ath.cx.invalid> - 2026-07-30 11:24 -0400
Re: Accumulator naming scott@slp53.sl.home (Scott Lurndal) - 2026-07-30 16:03 +0000
Re: Accumulator naming Rich Alderson <news@alderson.users.panix.com> - 2026-07-30 18:56 -0400
Re: Accumulator naming cross@spitfire.i.gajendra.net (Dan Cross) - 2026-07-30 23:48 +0000
Re: Accumulator naming John Levine <johnl@taugh.com> - 2026-07-31 01:31 +0000
Re: Accumulator naming cross@spitfire.i.gajendra.net (Dan Cross) - 2026-07-31 02:52 +0000
Re: Accumulator naming John Levine <johnl@taugh.com> - 2026-07-31 03:36 +0000
Re: Accumulator naming Lars Brinkhoff <lars.spam@nocrew.org> - 2026-07-31 13:40 +0000
Re: Accumulator naming Lars Brinkhoff <lars.spam@nocrew.org> - 2026-07-31 13:35 +0000
the Ten Heavenly Stems (was Re: Accumulator naming) Kragen Javier Sitaker <kragen@canonical.org> - 2026-09-11 16:07 -0300
Re: the Ten Heavenly Stems (was Re: Accumulator naming) Johann 'Myrkraverk' Oskarsson <johann@myrkraverk.invalid> - 2026-09-14 01:12 +0800
Re: the Ten Heavenly Stems (was Re: Accumulator naming) Kragen Javier Sitaker <kragen@canonical.org> - 2026-09-14 14:40 -0300
Re: the Ten Heavenly Stems (was Re: Accumulator naming) scott@slp53.sl.home (Scott Lurndal) - 2026-09-14 18:09 +0000
Re: the Ten Heavenly Stems (was Re: Accumulator naming) quadibloc@invalid.com (John Savard) - 2026-10-26 03:00 +0000
Re: Fizz Buzz "Kerr-Mudd, John" <admin@127.0.0.1> - 2026-08-21 13:27 +0100
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