Intersil Intercept Jr

Ethan Dicks ethan.dicks at
Thu Mar 5 11:29:49 CST 2009

On Wed, Mar 4, 2009 at 7:41 PM, Jeff Little (jeflittl)
<jeflittl at> wrote:
> To Whom it may Concern:
> What is all this stuff about the Intercept Jr?

Some of us still play with 12-bit machines, and some of us also have a
tube or two of IM6100s and the odd IM6100 lying about.  There's been
some on-and-off talk about designing a simple 4K IM6100 board that
would, by necessity, resemble an Intercept Jr.

> I was the designer of that little demo computer way back in the 1970s
> when I was working for Intersil.

Neat!  It's always great to hear from someone who was making the stuff
that we bought (or gazed at longingly, unable to afford).  I still
have a 1978 special issue of Popular Electronics I saved for the
Cosmac Elf article that also has a "complete" list of all micro
computers for sale at the time.  The Intercept Jr is in there, and I
remember it because it mentions PDP-8/e compatibility.

> If anyone get's this message, are there some specific questions you
> might have?

I don't have any specific questions, but I'm sure you have an
interesting story or two about tricks of the design or a manufacturing
issue or perhaps even of an "interesting" customer.

> There was also a larger version called the Intercept that I designed and
> we built first which was a full-blown PDP-8/E equivalent with 4K of
> 12-bit RAM, a full front panel, and a current-loop async serial
> interface that could be connected to an ASR-33 teletype and would run a
> full set of Digital diags and 4K-version software.

I think I remember reading about it, but I never saw one.

>  I believe eventually the Intercept
> was capable of running OS/8.   That required a 2-bank memory of 8K of
> 12-bit RAM as I recall.

Yes.  OS/8 does require 8K minimum.  I have a PDP-8/i I've been trying
to upgrade since I was in High School to be able to do more than run
paper tape on it.


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