14 Jul
2011
14 Jul
'11
11 p.m.
Thanks for the responses, the schematic from bitsavers is great.
Looks like some of the ROMs are special or proprietary devices, might
be a hassle to substitute.
I think I remember seeing the disk drive cabinet go out some years ago.
Still, looks like someone enthused about it could hack it into a
functioning PDP-8.
Is there enough of a ROM monitor to modify memory? If so, one might
fake the keyboard with a hacked serial connection from another computer
and download through the faked keyboard.
I think I'll put it on the bench to check out the monitor.
On 2011 Jul 14, at 6:19 PM, Vincent Slyngstad wrote:
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