24 Oct
2022
24 Oct
'22
3:13 a.m.
I'm really tired of P/OS being characterized as "a hack" or a
"bastardized
version of M-Plus". Probably 90% of the changes made were the named
directory support that was completely rolled back into the M-Plus stream.
The rest were changes to be able to run without DCL or MCR. And I believe
that ALL changes were reviewed or made by the M-Plus development group.
Chuck
On Sun, Oct 23, 2022 at 8:03 PM Steve Davidson <steve(a)davidson.net> wrote:
RT-11 was officially supported on the PRO series. The
PI(X).SYS handler
was the interface to the PRO specific hardware.
-Steve
SF:IP2
architecture. And a lot of that went poorly because Intel chips were used
for it, and Intel rarely if ever has good design for anything. The
interrupt controllers, for example, are a mess. Fortunately, most of its
misfeatures are not used on the Pro (like edge-triggered interrupts).
On Oct 23, 2022, at 10:56, Paul Koning
<paulkoning(a)comcast.net> wrote:
> On Oct 22, 2022, at 5:54 AM, Johnny Billquist <bqt(a)softjar.se> wrote:
>
> Well, obviously COPOS/11 isn't P/OS, as you later noted. :-)
>
> P/OS was the OS for the DEC Professions. Came in three models. 325, 350
and
380.
>
> The 325 and 350 were F-11 based. 325 only had RX50 floppies, while the
350 had
a harddisk.
> The 380 used the J11 CPU, but sadly at a low
speed and without cache.
And all software had to work with the F11 as well, so none
of the J11
improvements were used.
Basically, the Professional was a good idea implemented rather badly.
Its main problem was that it had a completely different I/O bus and I/O
The biggest blunder was a set of storage controllers without DMA, even
though the
bus actually supports DMA according to the documentation. So
the hard drives -- not very fast to begin with -- have to be 4:1
interleaved to avoid missing the next sector after an I/O is done. That's
true on both F-11 and J-11 based machines, so clearly the CPU speed is not
at fault.
On the Pro 380, a pile of discrete chips were replaced by one or two
gate arrays
(so many of those Intel chips disappeared, but not their ugly
APIs). Apparently, the designers made the I/O gate array at 10 MHz, and
made it synchronous with the CPU clock on the assumption that Harris would
deliver its promised 20 MHz J-11. When they did not (18 MHz was the best
they could do), the Pro 380 was forced to run the CPU at 10 MHz instead.
> And P/OS was a very bastardized version of RSX-11M-PLUS. Again, a good
idea
done badly. Menu driven, and weird. And not entirely compatible with
the rest of the RSX family.
There was also a Pro RT-11, I don't remember if that was an official
product
or a midnight project. The RSTS port was definitely a midnight
project.
And there were two Unix projects. I never remember which is which. One
made it
to field test -- I had that on my home machine -- but it was
canceled before the actual release, Then a different PDP-11 Unix was
shipped instead.
The field test one had some really weird hacks: I remember a "vi" that
didn't update the screen while you were typing, instead you had to hit some
special key to force the refresh to happen. My guess is that it was a
performance issue, but that seems strange because other software had no
trouble doing that sort of thing.
paul
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