This is brief listing of the microcomputers used by the Educational Technology Center up to mid-1983, including some statistics. The machines are presented in no particular order.
If the effort to rescue past dialogues and coding from their 8" discs is resumed, some knowledge of managing and communicating among these machines will be vital.
1. Terak 8510/a
The Terak is a microcomputer made by Terak Inc. of Arizona. Its CPU
chip is DEC's LSI-11, with the same instruction set as the PDP-11.
Teraks can have up to 4 disc drives; they are distributed with either
Remex or Shugart drives, single or double density. Although the single
density format is standard (8 inch discs are distrbuted in this format),
the double density is not, and only Terak can read it. The processor
boards are housed in the first drive, in the space above the
disc opening. The other drives house only their drive mechanisms.
Terak connector cables use an unusal, white translucent
plug with a square cross section, each shaped uniquely to its intended
socket. (Except of course for the disc drive connectors, which are
ribbon cables, daisy chaining as many drives as the installer cares
to attach, up to 4).
The settings of its serial ports are made with DIP switches on
the rear panel. CAUTION: the DIP switches tended to be FRAGILE,
and may not survive many changings.
CPU chip: DEC LSI-11 (16-bit), MACRO-11 instruction set.
Disc drives from 1 to 4, single or double density
Industry standard IBM 3740 disc format.
single density: 494 blocks
double density: 1140 blocks
(double density format is NOT standard).
MEMORY
capacity: 58Kbytes user accessible, 64K total
Remaining 8K is for the system's I/O
drivers.
addressing: byte addressed
memory byte sex: most significant byte first.
GRAPHICS Yes. The monitor can display any location
in memory as a screenful of pixels.
UCSD versions:
I.4, I.5, II.0, II.1, II.1x7b
2. ACI-90 (or Wicat) Western Digital MicroEngine.
This is the first machine to make the p-machine a real machine, rather
than a hypothetical one. The chip is an LSI-11, but with the p-machine
instruction set on it, rather than its usual MACRO-11. Western
Digital produced the chip; Associated Computer Industries (ACI) packaged
it, provided disc drives and I/O, and marketed it.
The major advantage of having p-code in hardware is the great increase
in speed over interpreted p-system versions.
CPU chip: DEC LSI-11 (16-bit), p-code instruction set
Disc drives 2, single or double density
single density: 494 blocks
double density: 988 blocks
Under versions of III release by Volition
Systems, the format may be changed by
software.
MEMORY
capacity: 64Kbytes or 128Kbytes, depending on version
addressing: word addressed
(therefore operations addressing individual
bytes are relatively slow).
GRAPHICS No. Requires that the terminal be capable
of interpreting graphics commands.
UCSD versions:
all subversions of III, which was created
specifically for the WD Pascal MicroEngine.
3. PDQ-3.
Using the WD Pascal MicroEngine (the chip itself), Advanced Computer
Design built the PDQ-3. It has 128K of user-accessible memory, the
popular Q-bus, and interrupt-driven I/O, which makes its I/O much more
reliable than the MicroEngine's (the PDQ, for example, has always had
full typeahead).
CPU chip: DEC LSI-11 (16-bit), p-code instruction set
Disc drives 2, single or double density
single density: 494 blocks
double density: 988 blocks
the format may be changed from the keyboard.
MEMORY
capacity: 128Kbytes user accessible.
addressing: word addressed
(therefore operations addressing individual
bytes are relatively slow).
GRAPHICS No. Requires that the terminal be able
to interpret graphics commands.
UCSD versions:
III.H0.
4. IBM Personal Computer
The IBM Personal Computer is intended for small offices and home users,
roughly the same market as Apple intended, but with a much better
machine. It uses the Intel 8086 chip, which is faster and much more
sophisticated than the 6502 used by the Apple (see below).
The keyboard is detached, weighted so that it won't slide, with very
light keys, including 16 function keys. The monochrome monitor has
80x25 characters, each with a 16x16 pixel font, which gives very good
character definition.
CPU chip: Intel Corp. 8088, 16-bit internally,
8-bit data bus,
with special string-handling instructions;
8087 numeric co-processor optional.
Disc drives 2, double density
320 or 400 blocks, depending on format.
Other drives available from many vendors.
MEMORY
capacity: up to 1 megabyte;
128K is user accessible, the rest is used
as RAM disc.
addressing: byte addressed
memory byte sex: most significant byte first.
GRAPHICS Yes, but requires a special monitor
(other than the system's monochrome monitor)
to display them. The graphics memory is
located on a separate board, so that it
doesn't use user memory.
UCSD versions:
IV.0, IV.1
5. Xerox 820-II
Xerox Corporation built this on the Zilog Z80B chip, an 8-bit chip with
instructions to allow 8-bit registers to be accessed in pairs, giving
quick simulation of 16-bits. Good for communications (terminals and
printers use the Z80), the 820-II is weak in arithmetic, since the Z80
has very few arithmetic instructions. The 820-II has a poor keyboard by
industry standards, and the disc drives are rather slow.
CPU chip: Zilog Z80B, 8-bits. Good I/O, weak
arithmetic.
Disc drives 2, single or double density
single density: 494 blocks (Terak format)
double density: 988 blocks
density is set at initialisation.
MEMORY
capacity: 64Kbytes user accessible.
addressing: byte addressed
memory byte sex: most significant byte first.
GRAPHICS No. Requires that the terminal be able
to interpret graphics commands.
UCSD versions:
IV.0
6. Sage II
Sage Technology, of Reno, designed the Sage II around one of the fastest
and most powerful chips currently available, the MC68000, which was
designed, among other things, for the implementation of high-level
languages. The first operating system they brought up on it was
UCSD IV.1. This is probably the most powerful machine ETC currently
has.
CPU chip: Motorola Corp. MC68000, 32-bit internally,
16-bit data bus,
with high-accuracy floating-point
instructions.
Disc drives 2, 5.25", fully software configurable.
Native Sage format:
double density, double sided: 1280 blocks.
Has preset formats for IBM, Rainbow, others.
MEMORY
capacity: up to 512 Kbytes,
128K user accessible, rest used for RAM disc.
addressing: byte addressed
memory byte sex: least significant byte first.
GRAPHICS No. Requires that the terminal be able
to interpret graphics commands.
UCSD versions:
IV.1
7. Rainbow 100
Shortly after IBM released the Personal Computer, Digital Equipment
Corporation released three personal computers: the Rainbow 100, the
DecMate, and the Professional 350. The least powerful of these,
intended for home use, is the Rainbow 100.
CPU chip: Intel 8086(16-bit) and Zilog Z80 (8-bit)
to allow software using either of them.
Disc drives 2 or 4, 5.25", with selectable formats.
Native format:
double density, double sided: 800 blocks.
MEMORY
capacity: up to 512 Kbytes,
128K user accessible, rest used for RAM disc.
addressing: byte addressed
memory byte sex: least significant byte first.
GRAPHICS A graphics board is supposed to be available
which gives the Rainbow graphics
capabilities.
UCSD versions:
IV.1
8. Apple II
The Apple is made by Apple Computer Inc., using the extremely small and
simple chip, the 6502 (also used by Atari and Commodore). This is an
8-bit chip, so the p-machine interpreter must use two Apple words to
make a single p-System word, which slows it down further.
The Apple can use 2 disc drives, with 280 blocks each. Although, with
memory extensions, some useful things can be done on the Apple, it is
not usually regarded as a serious working machine (although it is
widespread in homes, because of its price).
CPU chip: 6502, 8-bit word.
Disc drives 1 or 2, single density, 280 blocks.
MEMORY
capacity: up to 64Kbytes user accessible.
addressing: byte/word addressed
GRAPHICS Yes. High and low resolution graphics
with some colour capability. Lower
resolution than any other graphics machine
used by ETC.
UCSD versions:
II.1, Apple I.1, UCSD IV.0
9. TI 99/4A
Texas Instruments built the 99/4A around a proprietary TI chip, for home
use. It is the smallest system ETC has, and reputedly the smallest
system made on which the p-System will run. Most of the system,
including its memory, is composed of cartridges, which must be plugged in.
Not actively used by ETC at this writing.
CPU chip: TI propietary chip.
Disc drives none. (The p-System comes on a cartridge.)
MEMORY
capacity: Memory modules can be added to bring it up
to 64K
addressing: byte/word addressed
GRAPHICS Yes. High and low resolution graphics
with colour capability. Several graphics
pages, movable graphics planes called
"sprites".
UCSD versions:
IV.0