PDP-8 Minicomputer code Using Intercept Jr. with Intersil IM6100 microprocessor

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Intersil IM6100 microprocessor

The Intercept Jr tutorial system is an interesting microcomputer trainer that can execute the PDP-8 minicomputer code.  The design uses the  Intersil IM6100 CMOS 12 bit microprocessor. The idea of using the old PDP-8 code turned out to be a poor idea in 1976 and the computer and the IM6100 were never very popular. The PDP-8 was introduced 11 years earlier in March 1965 and used a 12 bit word.  The PDP-8 had a limited instruction set when you compare it to computers and microprocessors available in 1976. Most computer users moved beyond the PDP-8 minicomputer in the mid 70's.

The idea of a low power CMOS PDP-8 simulator just did not have any legs and died rather quickly. The 16 bit minicomputers & microprocessors were coming out with good computing power and of course 32 and 64 bit microprocessors in a few years.

The Intersil Intercept is colorful and nice looking - a beautiful display in our museum along with a full set of manuals. Like a most of the microcomputer companies of the 70's they went our of business when IBM came along with the Personal Computer (PC) in 1981.  A few companies did hang on and some new ones tried to get in the market but IBM was just to strong and Apple is the only USA company in business today- IBM also eventually gave up the small personal computer market. Apple has had it ups and downs however now it is the largest company in the world even bigger then General Motors.

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Intersil Intercept Jr.

The Intercept consist of a main board with CPU, octal displays and a keyboard for entering instructions & data.  The board ( backplane or mainframe) has three sockets for the CPU card, RAM card & ROM card.

The IM6100 CMOS 12 bit microprocessor is a static device and can operate with a clock frequency from DC to 2 Mhz.  Military versions can operate at higher clock speeds.

Intersil Intercept Jr.

The serial interface provides the user with RS232 and 20 mA current loop interfaces.

Intersil Intercept Jr.

The CMOS is very low power and the computer can be operated with on board batteries - 4 D cells.

Intersil Intercept Jr.

The keyboard is a membrane type and the keys can enter a full instruction with one keystroke.

Intersil Intercept Jr.

The RAM module uses (12) 1024 x 1 IM6518 chips for 1 Kilobyte of 12 bit words. Battery holders to power the module are on the upper right of  the board.

Intersil Intercept Jr.

the ROM/PROM contains 256 to 2048 words of program depending on which chips are used. The CMOS board uses only about .75 watts of power.








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Intersil Intercept Jr.

This is readable when enlarged and summarizes the 6100 family of CMOS chips and the Intercept Jr.








Jon Titus gave me this update on PDP-8 clones a few days ago.
"Hi, Dave.

Fabri-Tek also manufactured a PDP-8 clone, the MP12.  You noted in an early blog that Fabri-Tek produced a lot of core-memory modules, so they must have decided to jump into the computer market, too.  You can find a copy of the Fabri-Tek manual here: http://bitsavers.trailing-edge.com/pdf/fabritek/402-1001-00_MP12refMan_1974.pdf. Even after many years, the MP12 op codes look very familiar."

David Larsen

This computer is really colorful and just a beautiful display. It is also functional however we don't have many operational computers in the museum. Just not time to do  this and volunteers are hard to find in our little Blue Ridge Mountain town of Floyd, Virginia. We do have several vintage gaming stations operational and they are very popular. 

           .^{"by David Larsen"  KK4WW Computer Collector Historian} 

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Microcomputer - Micro-Designer MD-80 one of the first complete educational / design Microcomputer Systems

      John Titus tells about his designing the MD 80 microcomputer in the mid 70's

The Micro Designer 8080 (MD 80) microcomputer was the first system for training & development commercially available.  The system was a complete operational microcomputer with all the input/output signals easily available as solderless connections, training material  , and many operational software examples.

MD-80 by Blacksburg Group

 
   David tells little story about the origin of the very first complete training microcomputer

Dr. John Titus

This was the second major computer design for John Titus.  His first design "The Mark 8" computer was published in Radio Electronics (July 1974)  as a graduate student at Virginia Tech. The Mark 8 was also a milestone computer as one of the first constructions articles that made it possible for a computer geek to make his own affordable computer. This was 2 years before the Steve Wozniak's Apple 1. Here is the MMD-1 our second commercial computer and the first single board computer - another history maker for John.

MD-80 Micro designer

These were very exciting times for the group at Tychon blazing and leading the frontier in digital and microcomputer education. The group consisted of  Dr. John Titus , Dr. Peter Rony, David Larsen and later Dr. Chris Titus.

MD1 teaching in 1977

WOW I just found this 1976 slide using the MMD1 wired to an experiment when teaching an Interfacing Workshop.

MD-1

E and L Instruments Catalog

MD-1

Solderless breadboard Bus signals

The computer and educational material was marketed by E & L Instruments in Derby Connecticut.  I had arranged an agreement with E & L a year or so earlier to market the basic digital training system consisting of Bugbooks 1 & 2 along with digital training aids known as "Outboards".  This was about 38 years ago in 1975 and I remember my meetings with the E & L president Mr. Murry Gallent. This contractual arrangement provided our group had a nice royalty stream for about 10 years with many other books and hardware. The Group soon became known as the "Blacksburg Group".  E & L Instruments published the original Bugbooks . Fortunately we kept all the rights to the books and about a year later our publisher was "Howard W. Sams" and the books were known as "The Blacksburg Continuing Education Series"

See Micro- Designer computer (red) in the header on this blog - right side behind the word Museum.

David Larsen KK4WW

 The 10 years our group was creating books, microcomputers and digital training devices was a great experience for us. The 10 year path took many turns and most were positive and upward. We did have few bumps along the way.  One time E & L stopped paying royalties and were had an interesting and expensive lesson about litigation. Other than the cost of attorneys the royalties resumed from E & L.

^{"By David Larsen" KK4WW Computer Collector Historian}   
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