High-Tech Computing, Cafeteria Style
BYTE, Apr 1988, Mark L. Van Name
The CompuStar Theory of Sensibility (Advertisement)
BYTE, May 1989
The Bus Stops Here! CompuStar: PS/2 and PC/AT Compatibility (Advertisement)
PC Magazine, 28 Feb 1989
US4971563 Modular Backplane Assemblies for Computers (Google Patents)
CompuStar on The Computer Chronicles
Note: This page is mostly about the 80286 version.
Looks familiar... Is it a Dell???
Power switch, a reset button, a front panel lock, and a
four-character LED display. The LED shows both
diagnostic and system status information. For example,
"R" when reading the hard disk and "W" when writing to
the disk. If you press the Control or Shift keys, the
LED shows the current system speed.
You control the 80286 CPU Board speed with the Ctrl/Alt/+
combination to raise the speed, or Ctrl/Alt/-
to lower it. The system beeps once each time you lower
its speed, and twice each time you raise the speed. You
can also use a Wells utility, SPEED.EXE, to set the
speed from the DOS command line."
On the standard setup disk are DISP.EXE and SCROLL.EXE,
with which you can display four characters of your
choice, either statically or scrolling from right to
left, in the LED display. The Wells American ROM BIOS
was the CompuStar Multi-Processor Convertible
Microcomputer V l .05 BIOS ." (ed. which might be an AMI
All this AND a nice 8580-style handle!
Finally we can see where the CPU board is, in the center. A
snippet mentioned that the CPU board was fastened securely
on one end. My guess was that it used a ISA style slot
bracket on the rear end, and the front end slid into a tab
bracket like on a 95.
See the hard drive cables coming off the top AT card? That
might be an Adaptec ACB-2320 10-megabit-per-second ESDI
controller in the top AT slots.
"fans-one at the bottom front of the unit that blows out
enough air that you can feel it if you wear shorts, and one
at the top rear inside the power display case." [ed. PSU?]
Just a SWAG, but the "L" shaped board to the right of the
speaker and to the left of the Bus Modules -MIGHT- be the
"PS/2 adapter module". Note the AT bus only system lacks ANY
board to the left of the Bus Module socket area...
Notice the black connector sockets on the right edge of the
PS/2 module? The MCA Bus Module has a matching socket on
it's left side. Notice the single AT Bus Module -LACKS- a
socket on it's left side. But it doesn't need one, since the
CPU Board plugs into the I/O Module via the ISA riser.
I would guess that the MCA slots communicate to I/O Module
ports through the MCA contacts on the CPU card over to the
AT contacts, then down through the ISA riser.
Looking at this horrid quality image I would guess the AT
contacts are on the right, MCA contacts on the left. If you
glance up at the multi-bus system, you will see the possible
"PS/2 adapter module".
80286 CPU board is based on C&T NEAT chipset. Harris
Switch selectable 115v/230v 220-watt power supply
DB25 RS-232C serial port
DB9 RS-232C serial port
DB25 parallel port
PS/2-style 6-pin DIN keyboard connector
PS/2-style 6-pin DIN mouse connector
Rectangular opening between lower PS/2 connector and DB9
Video might be a board-mounted flip switch block to
configure the DB9 video port...
DB-9 digital connector
DB-15 VGA analog. VGA , EGA, CGA, MDA, and Hercules
Paradise PVGA1A chip
This board can handle up to four floppy disk drives.
|AT Bus Module
||MCA Bus Module
"The AT bus module has seven AT -compatible expansion slots,
while the PS/2 module contains five Micro Channel-compatible
slots and one AT-compatible slot."
"You can pick an AT- or PS/2 Micro Channel compatible bus
module; if you choose the PS/2 bus module, you also need a
special PS/2 adapter. The AT bus module has seven AT
-compatible expansion slots, while the PS/2 module contains
five Micro Channel-compatible slots and one AT-compatible
If you look at the top image of an open case, there is a
planar UNDER the top AT Bus module. As there was no second
Bus Module, you can see the planar's lower half. Note that
it does not extend past the black frame in the middle of the
Looking at the case images, you can see the push-pin
fittings, like in the 8570. Look at the patent drawings, and
you will see the snap fittings on the left end of the Bus
There must be some special mojo AT slot on the I/O module (I
prefer to call it a planar), and the "ISA" slot mentioned in
articles -MIGHT- be the riser which connects the AT bus
looking edge contacts on the CPU card to the special mojo
slot on the I/O planar.
I was thinking in two dimensions while the CompuStar used
that black frame as a standoff in order to mount another set
of PCBs above the I/O planar...
"So, in a single CompuStar chassis, you can have up to 13 AT
slots, or 10 PS/2 slots and one AT slot, or a mixed bag of
seven AT slots and five PS/2 slots." AT Bus Module has 6x
16-bit, 1x 8 bit, but the internal structure gets in way of
one slot so the limit is 13 slots. But there are only 11
externally accessible slots...
Interleaved memory banks, one bank of memory recharges while
the other is ready to go... nice improvement on traditional
two bank interleaving: If you have four identical memory
modules, it can do four way interleaving, so that three
banks are ready while one is recharging. On its 80386-based
CPU modules, interleaving is in addition to an Intel 82385
cache controller and 32K bytes of 35 ns SRAM cache.
"CPU module, which contains a CPU, a socket for a math
coprocessor, memory sockets, the ROM BIOS, sockets for two
expansion ROM chips, and a battery-backed clock/
The 8086 CPU board runs at 5 and 10 MHz and can hold up to
2.5 megabytes of RAM — and EMS 4.0 support is built onto the
board. The 8086 CPU board DOES NOT support the PS/2 Adapter
The 80286 CPU board runs at 20 MHz (with compatibility
speeds of 6, 8, 10, 12, and 16 MHz) and holds up to 16
megabytes of RAM (the second 8 megabytes require an extender
kit). Memory over 1 megabyte can be configured for any
mixture of extended (protected-mode) and expanded (EMS)
386 boards: 16 MHz, 20 MHz, and 25 MHz (each also runs at 10
MHz for compatibility). All 386 boards can hold up to 16
megabytes of RAM.
There will be a 386SX board as well, for users who need
32-bit computation without the expense of 32-bit memory.
All the CPU boards accept the standard Intel math
coprocessors; the 386 boards can also take the Weitek math
coprocessors. The 286 and 386 boards use 80 nanosecond
dynamic RAM; the 8086 uses 120 nanosecond DRAM.
The 80286 can run at 16, 12, 10, 8, or 6 MHz. Three
different oscillators (20, 16, 12 MHz) are divided by a
flip-flop divider in order to provide 10, 8, and 6 MHz
speeds. Control the speed with Ctrl/Alt/+ combination to
raise the speed, or Ctrl/Alt/- to lower it. The system
beeps once each time you lower its speed, and twice each
time you raise the speed. A DOS utility, SPEED.EXE, can set
the speed from the DOS command line."
Includes Wells's setup program (also in ROM and
accessible via the Ctrl/Esc key combination); a LIM/EMS
driver; system video mode utility; port assignments and
memory usage control (includes its use of interleaving and
shadow RAM); special disk drivers (including Extended
Diskette Drive BIOS); and the LED and compatibility speed
CompuStar Base Model 100 (huh: 90, 95, 100...)
AT-compatible primary bus module
AT-compatible secondary bus module
PS/2-compatible primary bus module
PS/2-compatible secondary bus module
PS/2 adapter module
8086 CPU module (does NOT support MCA Bus Modules)
80286 CPU module
80286 memory-extender kit
16 MHz 80386 CPU module
20 MHz 80386 CPU module
Processor: 20 MHz 16-bit Intel 80286; 10 MHz Intel 80287
Memory: 1MB 16-bit 80 ns DRAM on 80286 CPU module,
expandable to 16MB; 128KB of BIOS ROM
Size: 24 x 7.5 x 26 inches; 66 lbs (weight from 50 to 90
lbs, depending on configuration)