25 May
2011
25 May
'11
6:23 p.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