21 Oct
2005
21 Oct
'05
6:59 a.m.
On Thu, 20 Oct 2005, charlesmorris at direcway.com wrote:
Now that I have an apparently functioning PDP-8/A with
16K of core, and
(hopefully soon) a working RL02, I am wondering what operating system
would be appropriate. Currently I don't have any other input device
aside from the programmer's panel and the keyboard, so naturally I need
something that can be booted from an RL02...
Any recommendations? Will software written for, say, an 8/E or 8/I run
on an 8/A without patching?
Could I run OS/8? TSS/8? Many years ago I used to have access to a TTY
timeshared to an 8/E running Edusystem 50 (TSS/8) and would like that
"feel" again...
The only OSes I know of that supports the RL8A is OS/8 and RTS-8. For
OS/8, one RL02 will look like five disks (it's huge! :-) ).
Yes, as far as software is concerned, most everything written for an 8/I
or 8/E will also run on an 8/A.
I say most, since there are some incompatibilties that could bite you. But
then you're playing with undocumented opcodes, or hardware that is
optional.
However, the 8/E and 8/A are *very* similar. In fact, some 8/A systems had
the KK8E CPU in them.
Things that are incompatible, as far as I can remember offhand right now:
BSW instruction exists only on 8/E and 8/A.
MQ register exists always on 8/E and 8/A, but only exists on 8/I if you
have EAE. The 8/A cannot have an EAE. The EAE of the 8/E can run in two
modes, where one is compatible with the EAE of the 8/I.
If you execute a RAR RAL, you'll get different results depending on CPU. I
don't remember exactly what the 8/I does, but the 8/E will load the AC
with the PC for the high five bits, while the low seven will be fixed
(can't remember the exact value). The 8/A will load the AC with the PC.
But since all this stuff is things most programs don't do, it should not
bite you. (I know that KERMIT-12 uses these tricks to decide what kind of
CPU you actually are running on.)
Since RTS-8 is a bit magic, in addition to being a bit hard to get
perhaps, I'd say you should go with OS/8.
RTS-8 uses OS/8 for the interactive work anyhow, so you won't get much
extra fun out of it, unless you're really starting to write some special
software.
Johnny
Johnny Billquist || "I'm on a bus
|| on a psychedelic trip
email: bqt at update.uu.se || Reading murder books
pdp is alive! || tryin' to stay hip" - B. Idol
21 Oct
21 Oct
11:39 a.m.
QUOTE The 8/A cannot have an EAE UNQUOTE
Don't think this is correct. Because, such a machine would have no serious
(integer) arithmetic capability. Also, the PDP 8/A Minicomputer Handbook
1976/77 has a lengthy section [pp9-56 .. 9-65] on the KE8-E (Extended
Arithmetic Element : EAE). However, the "PDP-8 Summary of Models and
Options" (posted by Doug Jones) indicates that the EAE can be fitted iff the
PDP-8/E CPU boardset is fitted. That is PDP-8/A models 600/620 were fitted
with the KK8E CPU and optionally the 8/E EAE. And, I imagine "field
specials" were doubtless built.
Another wrinkle; correction invited.
Martin
-----Original Message-----
From: cctalk-bounces at classiccmp.org
[mailto:cctalk-bounces at classiccmp.org]On Behalf Of Johnny Billquist
Sent: 21 October 2005 12:00
To: cctalk at classiccmp.org
Subject: Re: Wondering which OS to use (PDP-8/A)
<< snip >>
Yes, as far as software is concerned, most everything written for an 8/I
or 8/E will also run on an 8/A.
<< snip >>
However, the 8/E and 8/A are *very* similar. In fact, some 8/A systems had
the KK8E CPU in them.
Things that are incompatible, as far as I can remember offhand right now:
BSW instruction exists only on 8/E and 8/A.
MQ register exists always on 8/E and 8/A, but only exists on 8/I if you
have EAE. <<<<NB>>>> The 8/A cannot have an EAE.
<<<<NB>>>> The EAE of the
8/E can run in two modes, where one is compatible with the EAE of the 8/I.
If you execute a RAR RAL, you'll get different results depending on CPU. I
don't remember exactly what the 8/I does, but the 8/E will load the AC
with the PC for the high five bits, while the low seven will be fixed
(can't remember the exact value). The 8/A will load the AC with the PC.
<< snip >>
23 Oct
23 Oct
12:49 p.m.
On 10/22/05, Martin Bishop <mjd.NO.bishop.SPAM at iee.org> wrote:
QUOTE The 8/A cannot have an EAE UNQUOTE
Don't think this is correct. Because, such a machine would have no serious
(integer) arithmetic capability.
The -8/a wasn't always sold to the same crowd as the -8/e. Lots of
-8/as were used for WPS/8 (the "DataSystems 310" package, for
example). Never doubt that Marketing is capable of selling systems
that aren't "serious". In any case, not everybody needs an EAE - I
myself have been using PDP-8s for 23 years, and with the sole
exception of wanting to put together a 12-bit SPACEWAR machine, have
never come close to needing an EAE.
There was an FPP-12 for the KK8A, but they were expensive (by PDP-8
standards) and rare (and not software compatible with the KE8E). If
you _really_ needed to boost FORTRAN performance, you had that option,
but to my recollection, it wasn't an ordinary add-on.
Also, the PDP 8/A Minicomputer Handbook
1976/77 has a lengthy section [pp9-56 .. 9-65] on the KE8-E (Extended
Arithmetic Element : EAE). However, the "PDP-8 Summary of Models and
Options" (posted by Doug Jones) indicates that the EAE can be fitted iff the
PDP-8/E CPU boardset is fitted. That is PDP-8/A models 600/620 were fitted
with the KK8E CPU and optionally the 8/E EAE. And, I imagine "field
specials" were doubtless built.
Another wrinkle; correction invited.
OK... to be pedantically specific... the KK8A CPU cannot have an EAE.
It's a single hex card with no "over the top" fingers to attach an EAE
to. I can't speak for the original poster, but frequently, folks
conceptually lump together the box name "PDP-8/a" with the most common
(of its day) CPU "KK8A" and thus the original statement is seen from
time to time.
-ethan
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