of Microprocessors

MICROPROCESSORS 133
further reduced by integrating all of the standard circuitry onto one
motherboard to which was added several S-lOO bus sockets for memory and
I/O expansion. Several of these machines even omitted the sockets (and the
power supply capacity needed to drive them), opting instead for a minimumcost
"standardized" computer.
Dozens of computers of this type were developed and introduced to the
marketplace. The lack of diversity and in many cases virtual identity led to
rhe first use of "clone" in magazine reviews of many of these systems.
Ultimate success became largely a matter ofwho could manufacture machines
at the lowest cost and market them most effectively. As a result, most of these
computers had relatively short lifetimes, many only a few months, and some
never went beyond the announcement stage.
Also during this time, the "original three" were upgraded to meet
business needs but still retained their architectural identity. Commodore
offered floppy disk drives for the PET and later upgraded its display from 40
to 80 characters per line. Apple also offered a disk drive and much improved
BASIC, although the display was kept at 40 characters. Interestingly
enough, independent companies developed Apple-compatible plug-in boards
to expand the display to 80 characters and changed the microprocessor to a
2-80, thus allowing the CP/M operating system and associated business
software to run. Radio Shack also offered disks for the TRS-80, but nothing
was ever done about the display, which was 16 lines of 64 characters. Also,
the architecture was not compatible with CP/M, even though a 2-80
microprocessor was used. However, since TRS-80s outnumbered other
microcomputers at the time, much business software was written specifically
for it.
There was also much activity in the home/hobby/education arena where
participation was more by established companies rather than new startups.
Atari, who had established themselves with arcade video games, offered their
model 400 and 800 computers. Packaged much like an Apple and even using
the same 6502 microprocessor, these machines were intended for a somewhat
less sophisticated audience. One new feature they offered was a ROM cartridge
slot that could be accessed without removing the cover or even turning the
power off The idea was that software packages could be offered on ROM in
enclosed "cartridges" that could be changed in the computer as easily as
cassette tapes are changed in a stereo system. Texas Instruments introduced
their 99/4 computer, which was intended for the same audience. Technologically,
it was a quantum leap past anything else at the time and
included a 16-bit microprocessor (the TI 9900), very sophisticated color
graphics IC, and four-voice sound (one might hesitate to call it music)
generator. Its sophistication was largely wasted, however, because the
machine's complex architecture was kept secret and TI software obscured its
inherent power. Amid much speculation about dominating the market,
Heath introduced a Z-80-based kit computer called the H-8. Although bus-