IM6100 (was Re: Computer Replicas)

From: Scott Stevens <>
Date: Wed Mar 31 03:00:10 2004

On Wed, 31 Mar 2004 04:56:56 +0000
Ethan Dicks <> wrote:

> On Tue, Mar 30, 2004 at 08:41:51PM -0500, Scott Stevens wrote:
> > I have a few tubes of IM6100 Microprocessor chips, which is the first
> > generation 'PDP-8 on a chip.'
> I have a tube as well (as do many of us, here and on the PDP-8 lists).
> What I'd like to know is if anyone has any hard info on the Intercept
> Jr. or the Jolt. I have brief descriptions in a 1978 Popular Electronics
> special issue in a section reviewing "all" of the available microcomputers
> of the day.
> That's all I've got. I know they aren't particularly powerful machines
> (ISTR without external logic, the IM6100 is limited to 4KW, among other
> issues), but I'd like to know more about them just the same.
> I also bought that tube of IM6100s in the hope that by the principle
> of "classic attraction", I'd run across a VT78... hasn't happened
> yet. :-)
> -ethan

I have (I think) a full set of the docs for the Intercept and Intercept, Jr. systems, and full datasheets for the IM6100 and the Harris second source part. My 6100 chips are actually the Harris part. I have it all converted into PDF files and if anybody wants it I can put it up on private webspace and post the URL (or email it). Or send out CDs.

The 6100 is quite limited, being it only addresses 4K of memory, but it's also extremely easy to put together a circuit for. It has really non-critical clocking requirements, you can even drive the clock in true 'single step' with a pushbutton or a 1 Hz clock if you like. Hook up a reed relay to the hamster wheel or what-not.

The 6120 is a much nicer processor to put together a 'real' single-board PDP-8 system. What I'd like to make out of a 6100 chip is a primative 'program with toggle switches and read LEDs' system that would recreate the experience of programming the PDP-8 at the switch panel in machine code. I'd envision a single-board with the processor, the blinking lights and row of switches, with a little memory, probably some of it battery-backed SRAM. Nothing more complex than that. I don't envision running FOCAL or an OS or anything complex on such a little thing. It would just be a cool 'toy' to dabble in machine code on toggle switches with. If others had more ambitious plans that would be neat, too, but this has already been done so nicely with the 6120 that it probably isn't worth it. Much as we can be nostalgic, 4K isn't a very big memoryspace, even with a 12 bit wordlength.

Received on Wed Mar 31 2004 - 03:00:10 BST

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