Josh Dersch wrote:
Hey all --
Picked up a DEC VT103 with an empty cardcage and I'm trying to decide
what manner of Qbus based system to put in it...
I understand it's possible to upgrade the backplane to 22 bits -- how
is this done?
I currently have a MicroVax 1 CPU, an 11/23 half-height CPU, a few
misc serial cards and the like, and a nice Emulex ESDI controller in
my box of spares... I'm worried about power consumption, though.
Anyone else hacked together a system like this and have any
recommendations for hardware/software?
Jerome Fine replies:
Power is DEFINITELY VERY limited - 16 amps for the 5 volts including
the video display card!!!!!!!!!!!
An M8186 is VERY possible. Use a DLV11-J strapped for the console
port. If you have the adapter
card to switch the terminals for port 0 and port 3, this makes it easy.
That also allows port 0 to be used
for a serial printer.
Check the Emulex ESDI controller for the power to be used. It is
probably OK. However, I STRONGLY
recommend that you use an additional PC power supply for the ESDI hard
disk drive if you are going to
run the system for more than a minute. Since the Emulex controller
probably has boot ROMs, you don't
need to type in a bootstrap each time.
Upgrading the back plane to 22 bits is easy and probably would take Tony
Duell only 15 minutes. It will
usually take everyone else a few hours. Wire wrap is probably the least
difficult to use with a small soldering
iron. You will need to use lead based solder. A total of 16 points
need to be soldered - 4 for each wire
to connect address bits 19, 20, 21 and 22. Leave the insulation on the
wire wrap except where the soldering
takes place. Probably Al Kossow has a manual with a diagram for the
VT103 back plane which show where
address bits 19, 20, 21 and 22 are located.
Using an M8190 quad 11/73 board is probably your best choice with as
much memory as possible. I would
suggest that you use a few memory boards as possible to keep the power
needed as low as possible. You
can also add the DHV11 or a DHQ11 to obtain 8 more serial ports. Add
the Emulex ESDI controller,
and external PC power supply for the drive with a fan on the drive since
those ESDI drives usually run hot.
Check the Micro Vax 1 for the power needed. Since it uses ordinary Qbus
memory, it should be OK. I am
aware that it is possible to make the first two slots ABCD to allow a
Micro Vax II, but I have no details.
With a PDP-11 CPU, I run RT-11. The normal problem of transferring
anything to the hard drive is the
problem. But the VT103 is a very nice small system. It was the first
system I ever owned and arrived
with an M8186, 256 KBytes of memory, DLV11-J and a DSD 880/8 hard /
floppy drive combo which
ran RT-11. Obviously, it was very slow compared to a PDP-11/73 and ESDI
hard drives with 4 MB
of memory, but I used it for many years for development work.
I still have the original box, but the DSD 880/8 failed about 20 years
ago and was replaced with a
DSD 880/30 and a PDP-11/73. I guess it has not been used for at least
10 years now.
Any other questions?
Sincerely yours,
Jerome Fine