"new" classics (was Re: Pre-history of Digital Research)

From: Richard Erlacher <edick_at_idcomm.com>
Date: Sat Mar 20 17:53:48 1999

I'm not so sure you're as far off-topic as you think. The connectors you
mentioned were all "old" technology back in the mid '70's when MITS and
IMSAI were pups. I'd submit that the DIN41612 connectors as used in VME bus
cards and in Apple Macintosh's NuBus are inexpensive enough today that your
can afford them. They're also 20 years old, as I was including them with my
VME wire-wrap boards in 1981-82. IIRC, the first run (20 boards) cost about
$19 per board for the connectors and mounting hardware. That's not much
more than the then-popular S-100's would have cost for 2 of each gender.

The notion of a front panel has often intrigued me, but recently I've
thought of using it more as a bus monitor probe, perhaps with an ethernet
connection to a PC and used for diagnosing functional anomalies. Instead of
discrete logic, it would use one or two of the SCENIX -SX processors and
drive the bus directly, loading memory and I/O features and storing the
monitored information in local memory for transmission to the PC host.
information could be displayed more effectively at the PC, but immediate
readouts in the form of discrete LED's, bit for bit, could be driven as
could HEX displays. The part I would view as important, however, is the
diagnostic function.

As for your loadable control store, I'd suggest you consider a mid-sized
FPGA. These can be loaded from a local processor and the architecture
changed at will, by reloading the device to suit the desired architecture.
if pinouts don't work, there are electrically reprogrammable crosspoint
switches routinely used every day, e.g. Lattice' GSX devices, to correct
unresolved routing problems, and there you are. You could actually fashion
your own processor right on your desk, but that really is off-topic.


-----Original Message-----
From: Chuck McManis <cmcmanis_at_mcmanis.com>
To: Discussion re-collecting of classic computers
Date: Saturday, March 20, 1999 4:18 PM
Subject: "new" classics (was Re: Pre-history of Digital Research)

>About every three weeks or so I kick around this idea of building a "new"
>classic computer. Lately my thoughts have been to build something with a
>loadable control store so that I could microprogram different instructions
>as I saw fit or was necessary. Of course the machine would have a front
>panel with switches and LEDs to indicate state.
>I then come to the question of "add in" boards. Ideally one would like to
>establish some sort of bus and make available a wide variety of add in
>boards that could be used to customize the system.
>Then there is cost, one would like to keep the cost at a minimum as well.
>So in the connector area I've been considering something "VME" like which
>would consist of two 50 pin right angle molex connectors and the
>"mainboard" would consist of 50 pin AMP sockets. These are pretty cheap
>because of SCSI and they should provide enough pins. (one could imagine
>three connectors for a total of 150 pins but that seems like overkill.)
>Unfortunately I think this is way off topic for this group.
Received on Sat Mar 20 1999 - 17:53:48 GMT

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