25 May
2011
25 May
'11
10:22 a.m.
So I finally got my hands on a pdp8/a at the University auction. It's the
omnibus model that's built into a desk and called the Classic, short for
CLASSroom Interactive Computer. I had no idea it was so heavy as it was
loaded for me into the back of my pickup. I discovered it must be real heavy
as the my F-150 groaned when loaded and when I came home and unloaded I
almost herniated myself. There it sits, almost complete (without the VT52)
but has an extra RL01/RL02 board. Is it the desk that gives it the weight. I
know the dual RX01 are heavy, but the are the cage, power supply and boards
real heavy in these things or is the DESK to blame. Until I put it on
something that I can move around, it will sit in my driveway. I can run a
terminal cable and an extension cord out to it to maybe boot it up after I
do some more research on it to see if all the boards are there.
One thing is not clear.n looking at the board numbers, it seems it doesn't
have a memory board, but it might have memory aboard the CPU card. Is this
right? It uses the newer cmos memory. It has the three board set that also
was used in the KIT-1, but it also has a variety of other boards that I'll
write down as soon as I can.
Cheers
Tom
25 May
25 May
11:22 a.m.
On 2011 May 25, at 10:22 AM, Tom publix wrote:
So I finally got my hands on a pdp8/a at the
University auction. It's
the
omnibus model that's built into a desk and called the Classic, short
for
CLASSroom Interactive Computer. I had no idea it was so heavy as it was
loaded for me into the back of my pickup. I discovered it must be real
heavy
as the my F-150 groaned when loaded and when I came home and unloaded I
almost herniated myself. There it sits, almost complete (without the
VT52)
but has an extra RL01/RL02 board. Is it the desk that gives it the
weight. I
know the dual RX01 are heavy, but the are the cage, power supply and
boards
real heavy in these things or is the DESK to blame. Until I put it on
something that I can move around, it will sit in my driveway. I can
run a
terminal cable and an extension cord out to it to maybe boot it up
after I
do some more research on it to see if all the boards are there.
Looking at some pictures
(http://www.piercefuller.com/library/10128.html?id=10128), if that
thick desk-top is made from particle-board (typical of office furniture
in that era) it would be a major contributor to the weight. (The unit
in the photos is on casters.)
Didn't one of the 8's use a ferro-resonant power supply, with a
consequently larger transformer core?
One thing is not clear.n looking at the board numbers,
it seems it
doesn't
have a memory board, but it might have memory aboard the CPU card. Is
this
right? It uses the newer cmos memory. It has the three board set that
also
was used in the KIT-1, but it also has a variety of other boards that
I'll
write down as soon as I can.
11:28 a.m.
On Wed, May 25, 2011 at 2:22 PM, Brent Hilpert <hilpert at cs.ubc.ca> wrote:
(http://www.piercefuller.com/library/10128.html?id=10128), if that thick
desk-top is made from particle-board (typical of office furniture in that
era) it would be a major contributor to the weight. (The unit in the photos
is on casters.)
That's the one I have. It is definitely heavy, even if you remove the
drives and the Omnibus enclosure (which is not easy to do with those
fans sticking out one side).
Mine has a dual RX02 and an RL01 as "drawers", a very useful
combination. I haven't fired it up in a long time, but back in
college, it was a daily-use machine (and took up a good chunk of the
dining room in a shared residence, to my housemates' dismay).
-ethan
11:23 a.m.
On Wed, May 25, 2011 at 1:22 PM, Tom publix <ittybittybytes at gmail.com> wrote:
So I finally got my hands on a pdp8/a at the
University auction. It's the
omnibus model that's built into a desk and called the Classic, short for
CLASSroom Interactive Computer.
Interesting. I have a desk-based -8/a that's badged as a DECsystem.
There it sits, almost complete (without the VT52)
but has an extra RL01/RL02 board.
Nice. Those are a bit unusual, but handy (the PDP-8 uses the same
packs as PDP-11s and VAXen, unlike with RK05s). Did you get the
cable?
One thing is not clear.n looking at the board numbers,
it seems it doesn't
have a memory board, but it might have memory aboard the CPU card. Is this
right?
That's not the usual arrangement. The "standard" -8/a order is...
M8315 KK8A PDP-8/A CPU board (hex wide)
M8316 DKC8AA PDP-8/A I/O serial/parallel/clock (hex wide)
M8317 KM8AA PDP-8/A bootstrap, powerfail (hex wide)
Then some amount of memory, in later models, commonly one or more of :
M8417 MSC8AA PDP8A 16K MOS Memory (hex wide)
M8417 MSC8AB PDP8A 32K MOS Memory (hex wide)
M8417 MSC8DJ PDP8A 128K MOS Memory (hex wide)
The M8417 comes filled three ways (that I know of) - half-full of
4Kbit DRAMs for 16K, full of 4Kbit DRAMs for 32K, and full of 16Kbit
DRAMs for 128K. Memory (and the KM8AA) goes in the slots with a
"fifth" backplane connector. That's where the extra EMA bits live
that permit expansion above 32K. You can mix and match memory cards
in those slots, but if you want to use install more than 32K, you'll
need the somewhat rare M8416 KT8A module (I only ever used it when I
was dabbling with RTS-8 and wanted a full 32K for my OS/8 task). If
you have 32K or less, things can go anywhere, but for cable routing
and bus termination and such, stick to the recommended order.
Here's a handy guide if you haven't found it already:
http://bitsavers.trailing-edge.com/pdf/dec/pdp8/pdp8a/EK-8A002-MM-02_PDP8A_…
(recommended population charts are on page 2-8, but the newer,
high-density MOS memory boards (and the KT8A) are newer than this
document).
It uses the newer cmos memory. It has the three board
set that also
was used in the KIT-1, but it also has a variety of other boards that I'll
write down as soon as I can.
It will be interesting to hear how yours is populated.
-ethan
4:40 p.m.
Great Find Tom!
One thing I'm not sure about is weather you have a 12 slot or 20 slot
box. The 12 has one G8016 or G8018, and the 20 slot (which is a LOT
heavier) has two of the regulators. I have memory boards, and if you
need any feel free to contact me off list.
Good Luck!
Paul
On Wed, May 25, 2011 at 12:22 PM, Tom publix <ittybittybytes at gmail.com> wrote:
So I finally got my hands on a pdp8/a at the
University auction. It's the
omnibus model that's built into a desk and called the Classic, short for
CLASSroom Interactive Computer. I had no idea it was so heavy as it was
loaded for me into the back of my pickup. I discovered it must be real heavy
as the my F-150 groaned when loaded and when I came home and unloaded I
almost herniated myself. There it sits, almost complete (without the VT52)
but has an extra RL01/RL02 board. Is it the desk that gives it the weight. I
know the dual RX01 are heavy, but the are the cage, power supply and boards
real heavy in these things or is the DESK to blame. Until I put it on
something that I can move around, it will sit in my driveway. I can run a
terminal cable and an extension cord out to it to maybe boot it up after I
do some more research on it to see if all the boards are there.
One thing is not clear.n looking at the board numbers, it seems it doesn't
have a memory board, but it might have memory aboard the CPU card. Is this
right? It uses the newer cmos memory. It has the three board set that also
was used in the KIT-1, but it also has a variety of other boards that I'll
write down as soon as I can.
Cheers
Tom
5:24 p.m.
Ok,
My initial brief inspection of boards, I missed one. It's the M8417 which is
the memory board. YEAH!!
So, The back plane is populated by the following boards, From top to bottom:
M8315
M8317
M8316
empty
M8417
empty
M8410
M8411
empty 3 slots
M8433
empty 3 slots
M842
empty
M8655
empty
M8357
It appears its a 20 slot back plane of course, there are a few empty spaces,
is this important on an omnibus back plane?, Or should the boards be
continuous?.
It seems that there are a rat's nest of cables balled up in the back cavity,
so I would assume all cables are present but I will unravel them all
tomorrow.
The console is one of the minimal consoles and not the programmers.
There is a broken latch on one of the floppy drives,
The desk has all four casters, but don't work well, I will need to put it on
a wheeled dolly anyway to move it around. Usually when I acquire a classic
computer in one piece, it means that it was working when taken out of
service. It's when parts are missing (probably cannibalized for other
working units) it usually means the computer did not work. Aside from the
monitor a VT50 (which may show up at another auction) was missing. It even
had some of the pdp handbooks. But alas, not OS/8 diskettes :-(
Cheers
Tom P
On Wed, May 25, 2011 at 4:40 PM, Paul Anderson <useddec at gmail.com> wrote:
Great Find Tom!
One thing I'm not sure about is weather you have a 12 slot or 20 slot
box. The 12 has one G8016 or G8018, and the 20 slot (which is a LOT
heavier) has two of the regulators. I have memory boards, and if you
need any feel free to contact me off list.
Good Luck!
Paul
On Wed, May 25, 2011 at 12:22 PM, Tom publix <ittybittybytes at gmail.com>
wrote:
So I finally got my hands on a pdp8/a at the
University auction. It's the
omnibus model that's built into a desk and called the Classic, short for
CLASSroom Interactive Computer. I had no idea it was so heavy as it was
loaded for me into the back of my pickup. I discovered it must be real
heavy
as the my F-150 groaned when loaded and when I
came home and unloaded I
almost herniated myself. There it sits, almost complete (without the
VT52)
but has an extra RL01/RL02 board. Is it the desk
that gives it the
weight. I
know the dual RX01 are heavy, but the are the
cage, power supply and
boards
real heavy in these things or is the DESK to
blame. Until I put it on
something that I can move around, it will sit in my driveway. I can run a
terminal cable and an extension cord out to it to maybe boot it up after
I
do some more research on it to see if all the
boards are there.
One thing is not clear.n looking at the board numbers, it seems it
doesn't
have a memory board, but it might have memory
aboard the CPU card. Is
this
right? It uses the newer cmos memory. It has the
three board set that
also
was used in the KIT-1, but it also has a variety
of other boards that
I'll
write down as soon as I can.
Cheers
Tom
5:53 p.m.
On Wed, May 25, 2011 at 7:24 PM, Tom publix <ittybittybytes at gmail.com> wrote:
Ok,
My initial brief inspection of boards, I missed one. It's the M8417 which is
the memory board. YEAH!!
There you go.
So, The back plane is populated by the following
boards, From top to bottom:
M8315
M8317
M8316
The KK8A, the KM8AA, and the DKC8AA - all standard. You might want to
check the M8317 for a pair of socketed ceramic DIPs. There should be
some letters and numbers stenciled on them that will indicate which
PROM set you have. There are three sets I know of, each with a
slightly different mix of bootstrap routines on them. Since you have
an RL8A (M8433), I think there is only one set with the RL boot on
them, so it's likely you are fine as you are. That set should have at
least RX and RL. It _may_ be documented with the RL8A manuals; I
can't remember for certain. It's newer than the 1978 minicomputer
handbook, so I don't think you will find the devices listed there.
M8417
You can check the handle for what variety of card this is, but since
you lack a KT8A, it's a good guess that it's either 16K (half
populated) or 32K (all populated).
M8410
M8411
An FPP8A. Never seen one, but I hear they are uncommon and desirable
(especially if you have a lot of FORTRAN-IV code to run).
M8433
Your RL8A.
M842
XY8E X/Y plotter control. I don't know much about it, but it might be
documented in the multi-volume PDP-8/e/f/m manual set.
M8655
KL8JA serial card.
M8357
RX8E - works with RX01 or RX02 drives.
It appears its a 20 slot back plane of course, there
are a few empty spaces,
is this important on an omnibus back plane?, Or should the boards be
continuous?.
Empty spaces are fine on the Omnibus.
It seems that there are a rat's nest of cables
balled up in the back cavity,
so I would assume all cables are present but I will unravel them all
tomorrow.
The console is one of the minimal consoles and not the programmers.
That's common, especially in the desk where you normally can't reach
the front panel. Since you have two kinds of mass storage and a
bootstrap board (a typical arrangement), ordinary operation is to halt
the machine and toggle the bootstrap line to bring up whichever device
is selected on the KM8AA. It's a bit of a pain to switch devices, so
if you have floppies that need to be booted, one way to handle that is
pick the RX8E and have a standard OS/8 diskette you can use to re-boot
via software to bring up a drive on the RL8A.
There is a broken latch on one of the floppy drives,
Unfortunate. The RX drives are Calcomp mechanisms, which were once
common, so perhaps you can find a replacement latch or carriage
assembly.
The desk has all four casters, but don't work
well...
Unfortunate. ISTR the casters pull out of the tubular legs fairly
easily (I needed to do that to let the desk fit in a station wagon.
Perhaps you can pull the casters and recondition them.
Aside from the
monitor a VT50 (which may show up at another auction) was missing. It even
had some of the pdp handbooks. But alas, not OS/8 diskettes :-(
The VT50 is, in my experience, less common, but also less desirable
for regular use because it only has enough internal memory for 12
lines of text (vs 24 lines for the VT52). You will probably find it
easier to lay hands on a newer DEC terminal and use the built-in VT52
emulation. I don't recall any OS/8 programs written for VT100 escape
codes, but any that do more than just scroll text will be written to
send VT50/VT52 escape codes.
Sounds like a great system.
-ethan
4964
days inactive
4965
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6 comments
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participants (4)
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ethan.dicks＠gmail.com -
hilpert＠cs.ubc.ca -
ittybittybytes＠gmail.com -
useddec＠gmail.com