From simasd!nosc!CRDEC2.APGEA.ARMY.MIL!pvpullen Thu Sep 20 06:05:03 1990
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Date:     Thu, 20 Sep 90 7:24:43 EDT
From: "Paul V. Pullen" <pvpullen@CRDEC2.APGEA.ARMY.MIL>
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Cc: pvpullen@CRDEC2.APGEA.ARMY.MIL
Subject:  Intertec Compustars
Message-Id:  <9009200724.aa25505@CRDEC2.APGEA.ARMY.MIL>

Don,

Intertec manufactured four versions of the Compustar computer.  They were 
equipped for setting up multi-user 'networks' using either a 10 megabyte or
80 megabyte hard drives.  They are all equipped with the usual modem and 
auxillary ports on the back panel, as well as two ~35 pin d-type connectors
that attached the systems to the hard drives.  Each unit is equipped with an
additional board called a chaining adaptor that enables the units to 'chain'
together and use the common hard drive.  It was a good idea for software, and
then had you use a floppy (?) for your data.  

Intertec's design included the use of a hardware switch on the chaining adap-
tor that enabled the system to have a maximum of 255 different 'stations' on
the 'multi-user system'.  Each station would have its own section parsed out
of the hard drive, an individual drive c: assigned to the terminal.  If it
did not have an 'area' carved out of the hard drive, the system would not allow
the station on the network.  We used a maximum of 4 stations at one time on our
network when it was operational.  It seemed to work pretty well.

Intertec manufactured the following models in the Compustar line:

	VPU-10	This model was a terminal only.  It required its operating
		system to be written to the system tracks of the hard drive.
		There were no floppy drives on these terminals.  I guess it
		would be considered the system console.

	VPU-20	This model contained either one or two (I never saw one of
		these) Single sided disk drives.  What little I know is from
		an enhanced piece of software that formatted disks especially
		for the systems 20,30, and 40.  If I recall correctly, it uses
		drive a: to format the disk, so I suspect that the VPU-20 only
		had one disk drive.

	VPU-30  This model comes (or came) in at least two versions.  I have 
		samples of each, both personal and government owned.  The 
		systems contained two DSDD disk drives, and could be booted 
		either in stand-alone mode (no hard drive) or in networked 
		mode.

	VPU-40  This model contained the 96 tpi drives.  I have never seen one.

I will check for ROM versions, but the easy way on the VPU-30 to tell the diff-
erence between them that I know is two fold.  First, the power supply on the 
non-enhanced VPU-30 is mounted on the bottom chassis.  It is tied together with
the main circuit board by a flat cable that is made up of strips of 'aluminum 
foil' in vynal jacket.  It truely is a flat cable.  This model of computer uses
Magnetic Periphals disk drives (NEVER use a Tandon Drive in this version.  The
current draw of the Tandon will blow the power supply).

The smarter VPU-30 has its power supply mounted on the back of the disk drive
cage.  It has a larger power supply and was stocked with Tandon TM100-2 disk
drives.  It needs a different operating system than the non-enhanced.  Another
difference is the real-time clock battery mounted on the upper right hand 
corner of the main circuit board.  The circuitry is different on the boards,
but both would maintain a clock in the upper right corner of the tube.  The
enhanced would, like the present pc-clone, maintain the time even when turned
off.  The enhanced version of the VPU-30 was equipped to maintain the time, 
whether the system was off or on.

If I recall, the ROMS never had marks on the outside as to what their ROM 
revision was.  We had problems with this and the hard disk DSS-10's.  I have
two personal DSS-10's with different ROMS in them.  It is terrible to
re-initialize.  By guess and by gosh I have re-initialized them, but you 
have to play with the computers to find one that will talk to the disk drives.

This is a first run of information that you can store.  I will assemble the
boot disks and get them out to you as soon as I can put them together.

Paul

----------------------------------
Paul Pullen
United States Army Chemical Research, Development and Engineering Center
pvpullen@crdec2.apgea.army.mil
(301) 671-2519 /(301) 671-4174			
----------------------------------
