14 Jul
2011
14 Jul
'11
6:19 p.m.
From: "Brent Hilpert": Thursday, July 14, 2011 5:20 PM
Speaking of VT-100s:
Received a Decmate I / VT278 recently (PDP8 micro in VT100 cabinet),
sans keyboard and disk drives. I don't really expect to hang on to it,
but I'm a little curious to assess it some.
I suppose a keyboard may not be too difficult for
someone to obtain,
the disk drives I expect will be less likely; or can anyone comment on
what it will take to make this a half-way-useable PDP8 system?
I think you are looking basically for a VT-100 style keyboard, though
the authentic one would have the "Gold" key in the upper left of the
keypad.
As for "disk drives", the standard thing is a pair of RX01 floppy
drives, interfaced with a slightly different cable. To be completely
authentic they should be in a tower that is holding the VT278 up
at desk height :-).
I expect that RX02 with the internal switch set for RX01-only mode
should also work fine. RX02 were used on a lot of PDP-11 systems,
and so aren't too difficult to find.
I suppose one of the 6402s drives the printer port,
what does the other
do? The COMM-ports board that sits beside the processor board is
missing. Any problem with blowing ROMs to turn the printer port into a
boot/download port?
Have a look at the drawings at
pdf/dec/pdp8/cmos8/
on your favorite bitsavers.org mirror.
From what I can see on MP00900_VT278_may81.pdf 40/74,
it looks like
E46 is the COMM-port and E45 is dedicated to a serial intefrace to
the
keyboard.
When powered on the PWR-OK & CPU-OK LEDs light up
and the CRT filament
lights up, but there is no sign of any raster. Kind of looks more like
the monitor is dead (no trace of beam when powered down for example). I
take it (due to absence of physical controls) brightness and contrast
are software controlled (I didn't remember VT100 class stuff being like
that). Anybody happen to know whether a bare Decmate like this (no
keyboard, no disk drives) should display anything on-screen upon
power-up?
I'd have to look into that. The DM II and DM III display an error code
on the screen, but I don't know offhand about the older VT-278.
Vince