Your IBM Computer, June-1984
by Lloyd Borrett
Your Computer, June 1984
Though I've always freely revealed my background and
interests to those who ask, some recent events highlighted
the fact that I'd not done so to the readers of this column.
So here goes.
I've been employed as a member of the information systems
department for BHP in Melbourne for over seven years. I
started out cutting code in BASIC and Fortran on Data
General mini-computers for the Mine Planning, Oil and Gas
Exploration, and Minerals Exploration systems.
Later, systems support for Data General minis became my
full-time role for some three years. The highlights of this
period were the introduction of an X.25-based computer
network, the move to the AOS/VS 32-bit virtual operating
system, an office automation pilot, and a term as president
of the Data General Users Group.
During the fourth quarter of 1982 I purchased my own
IBM-PC, with the intention of implementing some software
packages I'd designed. Instead, I ended up consulting for
small businesses and writing articles for Your Computer.
This was, and still is, done as Lloyd Borrett, private
citizen, It has no connection with BHP. In March 1983 I was
appointed Personal Computer Co-ordinator for BHP Melbourne.
Late in 1983 I stopped taking on consulting work to
concentrate on two other projects. The first was starting
the Melbourne PC User Group (MELB-PC). That group is now
going strong. I currently serve as president and assist in
the production of the group newsletter. Although MELB-PC is
trying, and I believe succeeding, to carry out its
activities in a professional and business-like manner, it's
a non-profit user group like most others.
My second project was to start a mail order business,
supplying hardware and software for IBM and compatible
personal computers at discounted prices. That company, PC
Connection Australia, is now becoming widely known but it
remains only a part-time interest for me. The company's goal
is to introduce some sanity to the pricing of PC products in
Australia, and to provide a high level of technical support
for a selected range of the excellent products available.
Some people have thought MELB-PC is a group for BHP
employees, others have thought PC Connection Australia is a
business arm of MELB-PC. I hope the above revelations will
serve to clear up such misconceptions. Now you also have
facts to decide if I have a vested interest in any issue.
How Compatible Is Compatible?
The reports made by microcomputer industry observers on
the COMDEX exhibition held late in 1983 all came to the same
major conclusion the IBM Personal Computer has become the de
facto standard of the industry. When IBM introduced the PC
in 1981, many companies began providing products for the new
machine. Now there is a huge array of hardware and software
for the PC. This has boosted sales of the PC, and as a
result more companies have been induced to design and
introduce more products.
At the same time, some firms have created a new market in
PC compatibles. IBM's inability to manufacture enough
product, and the newcomers being able to offer lower prices
and portability, have been key factors in the success of the
PC clones. Essentially these sell because they are
compatible with the IBM-PC and can use products designed for
the IBM-PC. But how compatible is compatible?
There are levels of compatibility, and at present it
seems a lot of advertising is playing on people's
misconceptions, laziness and ignorance of this subject. A
truly compatible machine would be illegal. It would be a
physical and electronic copy of the IBM-PC. Already IBM has
been successful in moving against Corona and others for
There must be differences between an IBM-PC and a machine
claimed to be compatible. Also, there must be differences
between each of the so-called compatible machines. So in
order to claim PC compatibility, the manufacturers vary
their interpretation of the word compatible. Currently, it
seems we have both illegal copies and machines which have
nothing more in common with the IBM-PC than an Intel 8088
compatible chip in the enclosure.
Levels of PC Compatibility
Level 1: Media compatible. These are machines
which have the ability to read and write disks in the
formats used by the IBM-PC. The NEC APC, DEC Rainbow 100,
Dot, Hewlett Packard HP-150, and Sirius are examples of
machines which are not media compatible.
Level 2: Processor compatible. These machines use
a microprocessor chip such as the eight-bit bus 8088 and
80188, or the 16-bit bus 8086, 80186, and 80286. If done
properly, such substitutions need have little effect on
compatibility. The more powerful chips can perform some
operations faster, which may cause problems for some
timing-sensitive software. The Apple Lisa, Olivetti M20, and
DEC Professional 350 we not processor compatible.
Level 3: Operating system compatible. These are
machines which support MS-DOS or IBM's variant, PC-DOS.
Nearly all the software for the IBM-PC uses PC-DOS, with
most also being made available under MS-DOS at a later date.
Machines that offer only CP/M, CP/M-86, P-System, UNIX and
other operating systems are not operating system compatible.
Level 4: Component compatible. These machines can
use the add-on circuit boards designed for the IBM-PC. The
Wang PC, Zenith Z-100, and TI Professional are not component
Level 5: Character set and keyboard compatible.
Such machines display all the 256 character codes used by
the IBM-PC and have keyboards which include the same keys as
Level 6: Video compatible. IBM-PC displays are
memory-mapped. Video compatible machines must use the same
video interface and memory addresses as used in the IBM-PC.
Level 7: System compatible. These machines
duplicate the entire architecture of the IBM-PC. All I/O,
RAM, ROM and other addresses, including the routines in BIOS
and BASIC ROM, must reside at the same locations as in the
Most successful PC clones fit into the third level. They
use the same disk format, an 8088 or 8086 chip, and MS-DOS.
Some, such as the COMPAQ, Columbia, Corona PC, Hyperion,
Eagle PC and Chameleon, achieve higher levels. To meet Level
7 would incur the wrath of IBM.
The manufacturers' reasons for trying to emulate the
IBM-PC are obvious. But before you choose a PC compatible
you must sort out your own motives. Work out which software
you need and what level of compatibility those software
products require. Consider your requirement for add-on
circuit boards and peripherals.
Simply calling a machine IBM-PC compatible unfortunately
doesn't make it so. Be very careful of compatibility claims.
Saturday, 15 October 2011