Imsai Vdp 40

From: Jack Peacock <peacock_at_simconv.com>
Date: Sun Aug 16 14:44:07 1998

>Has anybody heard of the Imsai Vdp 40 machine? What is it, and
how many have been made?

Not sure how many were made, but the VDPs came out in the late 70's,
around '78 or '79 as I remember. I bought several to use as special
purpose POS terminals in a casino. They were in a "standard" size
IMSAI/S-100 case, but they had a short motherboard (8 slot? have to
look) and bays for two full height 5.25" floppies. Typically they came
with an IMSAI 8085 CPU card, a two board floppy controller (not very
reliable), PerSci floppies, and a 64K DRAM memory board. The power
supply was scaled down from the big 500 watt version, plus it had an
extra regulator board for the floppy power. There was no front panel,
just two buttons, RESET and INT (I think this was connected to one of
the S-100 interrupt lines), and a power switch.

IIRC there were three basic models, the /40, /42, and/44. The 44 was
the high end, full 64K and the fast PerSci disks. Just before IMSAI
folded, they were offering a hard drive interface to some type of 5MB
top loading drive (I think it was some CDC drive equivalent to the DEC
RL02), at least the salesman called and tried to sell me some, but I
never actually saw them. IMSAI was famous for it's vaporware.

System software was CP/M 2 with NED (aka WordMaster), a nice video
terminal oriented editor.

I still have one, though it does need a little work on the motherboard.
How I got it was an interesting story in itself. Originally I had
bought four of them for a customer, in late '78, just before IMSAI
folded. After they were installed I didn't have too much contact with
the customer, but I knew they were in use for several years. About 12
years later a friend of mine came over one night, dumped a VDP40 on my
table and said I could have it. He had paid $5 for it at a yard sale,
knew I had some IMSAIs, thought I might want it. I opened it up, and to
my suprise found the custom serial card I had wired for the original
customer still in there, it was one of the original VDPs I had bought.
No idea how it wound up at a yard sale.
    Jack Peacock
Received on Sun Aug 16 1998 - 14:44:07 BST