-----Original Message-----
From: cctalk-bounces at
classiccmp.org [mailto:cctalk-
bounces at
classiccmp.org] On Behalf Of Marc Howard
Sent: Monday, January 06, 2014 11:24 AM
To: General Discussion: On-Topic Posts Only
Subject: Easiest way to get MAINDEC diags onto a PDP-8 (sans paper tape)
Hi,
I've been bringing up a PDP-8a system over the past few months. It has 2 x
TU56 (TC08 controller), 3 x RK05J and a 3rd party RX01 dual floppy. The
processor itself is an 8e board set w/EAE and 32K core.
As for media I have 7 RK05 packs, one floppy and about 60-75 dectapes.
My first attempt at booting was with the RK05. It took a ton of cleaning (and
capacitor replacement/reforming) to bring up the 8, followed by cleaning one
of the RK05 drives. (BTW, this stuff apparently was in the equvalent of a barn
for at least 20 years by what I could see).
Anyway I cleaned 2 of the RK05 packs that seemed most likely to be bootable
media but no joy. The drive just seeks to cylinder 0 and sits there, although I
think a data transfer *might* have occured. I suspect that all of the RK05
packs were for individual user backup. Apparently from the documentation I
have this system at one time had a RL01 attached.
Next I worked on the better looking of the two TU56's. I've got one drive
shuttling okay; the other half has no torque in one direction; I suspect I need
to replace yet another AC motor run capacitor.
The TC08 checked out okay and I replaced all of the das blinken lights with
new bulbs, it looks really cool.
Then the big test. I picked out a tape that had a listing with it indicating that it
was a system tape of some sort (Focal, editor, etc.)
I toggled in the TC08 boot code (since my M8317 has the wrong boot roms for
it) and hit run. The tape wound back to the beginning, reversed, seemed to
transfer many blocks of data and then just spins in a loop.
So the next step would obviously be to run some TC08/TU56 diagnostics but I
don't have any way of loading them.
If I had an RK05 pack with OS8 + diags on it that would work but I don't see
that happening. Perhaps another alternative would be to get the equivalent
on RX01 floppies from someone, but I don't even know if the floppy system
works yet.
So for now I think figuring out how to make a combo terminal emulator/raw
data file thingy might be the best way to go. I'm thinking of putting a
beagleboard to use for this unless anyone out there has a simpler/quicker
solution.
Suggestions anyone?
When I was bringing up our 8/e, the last idea you mentioned is what I did, just from a
laptop with a terminal emulator and use David Gesswein's sendtape program to load
diagnostics from papertape image. The TC08 has several adjustments that can easily get
out of trim, and the standalone diagnostic for it includes several scope loops to make it
easier to adjust those. Of course, you still have to sort your way through a gazillion
wirewrap pins and get the scope probe on the right one.... -- Ian