24 Oct
2022
24 Oct
'22
3:41 a.m.
Nah. There were/are more things. P/OS have some weird services that take
care of mounting and unmounting file systems as some kind of automated
thing. There are some additional system calls. It has some kind of weird
variant of named directories, where you actually have a hidden
hierarchical directory structure, which is really strange, and don't at
all exist in RSX. And, as you mention, the sortof ripping out of
MCR/DCL, which isn't complete. Much of the kernel source code is shared
with RSX, but the additional tasks and services are not, and I've never
seen the sources of those.
But if I try, I can probably remember more things about P/OS which are
different.
Johnny
On 2022-10-24 03:13, Charles Guldenschuh wrote:
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
<mailto:steve@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
--
Johnny Billquist || "I'm on a bus
|| on a psychedelic trip
email: bqt(a)softjar.se || Reading murder books
pdp is alive! || tryin' to stay hip" - B. Idol
On Oct 23, 2022, at 10:56, Paul Koning
<paulkoning(a)comcast.net
<mailto:paulkoning@comcast.net>> wrote:
> On Oct 22, 2022, at 5:54 AM, Johnny Billquist <bqt(a)softjar.se
<mailto:bqt@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
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).
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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