Intersil Intercept Jr

[Jeff Little (jeflittl)]

Ethan:
I can tell you that the Intercept Jr. was built, not in a regular factory setting, but in a sort of glorified lab that we put together on the ground floor of the same building in which the fab line for the 6100 existed.  That location was later abandoned by Intersil when it was purchased by Harris Semi and was declared a federal toxic clean-up superfund site.  It appears that the underground tanks in which Intersil stored it's cleaning solvents from the fab line leaked and contaminated all the ground around.  The building itself sat empty for almost two decades and then was demolished in the late 1990s.  Today it is a large patch of gravel on Tantau Avenue in Cupertino, California.  

The Intercept Jr. was originally conceived as a demo and educational product to promote the IM6100.  A series of classes to teach assembly language programming were developed that used it as the primary lab tool.  It was inspired by the KIM-I single-board computer, if you remember that unit.

The most interesting application for it that I can recall was the adaptation of the main board by a team of geologists working at the Menlo Park US Geographic Survey office to be the heart of a remote data collection device for seismic sensors that were placed up and down the San Andreas Fault.  The extreme low power consumption of the IM6100 made it ideal for battery-driven applications and the compatibility with the DEC PDP-8 meant that the scientists were comfortable with programming it.

The success of the IM6100 itself was always limited.  Intersil opted for PDP-8 compatibility and struck a deal with Digital to do the microprocessor version so that developers would have access to the rich PDP-8 SW library, including TECO (an early word processor), OS/8, spreadsheet-like programs, BASIC, FORTAN, C compliers, a programmable calculator that ran in under 4K whose name escapes me at the moment, and a whole lot more.  Intersil, which was a fairly small outfit at the time, did not have to do any real SW development of its own.  I and my boss (Thampy Thomas, later founder of NexGen) were the entire SW team for the IM6100 and we did it in our spare time because our first responsibility was to be the applications support team for the product.  The total transistor count in the IM6100 is around 4000, which is nanoscopic by today's standards.  I personally did a lot of the mask checking for the product by hand with colored pencils and a magnifying glass.  The design lead engineer for the IM6100 project was a gentleman named Frank Shenstrom.  He was laid off by Intersil shortly after the design was completed during the next semiconductor down-turn, around 1976.  The engineering manager for the project was a fellow named Shep Hume.

Unfortunately, Digital just could not be convinced to let the SW be used for the low prices needed to attract potential personal computer users (though we didn't call them that at the time).  They still charged license fees that were sized for the mini-computer market, not the micro.  The PDP-8 was very mature at the time and giving the SW away for free would have cost them little revenue loss on their PDP-16 and coming VAX products.  There was one fellow I remember who was working on building a low-cost 8K machine as a future product.  His design could have been the first really popular personal computer if DEC had just been able to see the light on SW pricing.  The history of the personal computer could have been quite different if that had come to pass.

Regards,
Jeff

PS:  It is interesting to note that I was working for Compaq at the time that they acquired what was left of DEC many years later.  How the mighty had fallen.

  

-----Original Message-----
From: Ethan Dicks [mailto:ethan.dicks at gmail.com] 
Sent: Thursday, March 05, 2009 9:30 AM
To: Jeff Little (jeflittl); cctech at classiccmp.org
Subject: Re: Intersil Intercept Jr

On Wed, Mar 4, 2009 at 7:41 PM, Jeff Little (jeflittl) <jeflittl at cisco.com> 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.

-ethan