27 Oct
2010
27 Oct
'10
1:27 p.m.
-----Original Message-----
From: cctalk-bounces at classiccmp.org [mailto:cctalk-
bounces at classiccmp.org] On Behalf Of Johnny Billquist
Sent: Tuesday, October 26, 2010 11:40 PM
To: cctalk at classiccmp.org
Subject: Re: Happy Birthday VAX 11/780 (influence of)
On 2010-10-27 06:20, William Donzelli<wdonzelli at gmail.com> wrote:
I honestly don't know.
The PDP-11 have been attributed with the common I/O and memory bus
(Unibus), with memory mapped I/O as well as the concept of condition
codes. Also the general registers with a nice set of addressing modes
to
use on them. And we should probably not forget having the PC as just a
general register (although few, if any, picked that one up). So the
PDP-11 can be used as a accumulator-based machine, a memory-memory
based
machine, or a stack based machine. It's possible to implement all
concepts found in architectures at that time easily on the PDP-11.
The basic PDP-11 architecture was deigned so that if an instruction
took
an argument, any kind of argument was equally valid.
But as usual, the question is: was really the PDP-11 first with these
things, or can you find earlier examples?
I do believe the PDP-11's use of memory-mapped I/O was original - at least I can't
think of any earlier examples. -- Ian
> > 1.> The PDP-11 was in architectural
ways more important than the
VAX, if
> > ?> nothing else than just because
the VAX was basically just
extending the
>
?> PDP-11.
Just to throw another question into the fire:
Just how important was the PDP-11 or VAX-11/780 hardware architecture
in the grand scheme of things? Did either machine really bring
anything new to the table?