Modcomp Computer?

On Tue, 30 Aug 2005 16:07:04 -0700 (PDT), Jeff Davis" <jdaviscl2 at soupwizard.com> wrote: [...] What you found was a Modcomp II, a 16-bitter with 64 kwords of memory. The machine was modeled (ala SEL) on the IBM 1800 series controllers and were used primarily in communications and process control. There were produced in the 1974-78 period, or thereabouts. The design was interesting in that it used microcode which could be extended through a microword bus. Consequently, unused instructions were used for floating point, communications controllers, etc. OS was multi-tasked, priortized, and fully pre-emptive. The file system was ala IBM: you allocated your files at sysgen time. They were quick machines for the time. There is a knob on top of each plane which when pulled up allows the plane to swing open. By far the easiest computer to work on I've run across... IIRC all the planes, with the exception of the memory were wire- wrapped and all ICs are socketed. What makes these planes unique is that the power regulation is at the top on each plane. Raw DC is provided from some honkin' supplies located at the back of the drawer. The original IIs were implemented in 74Hxx (read very hot, but not too fast) and consequently there are IIRC 9 fans on the bottom of the drawer. Generally, I/O was housed in plain boxes beneith/along side the computer, but constructed with the same planes as the main computer. However, these planes were oriented horizontally. I ran one in an experiment during the period 1975-78. It was mounted in a trailer which traveled over 10k miles over the period of the experiment - damn reliable beast. I would love to see some pictures :-)) CRC