The Best of Creative Computing Volume 1 (published 1976)
Building a Computer of Your Own (microcomputer kits)
During the last year, getting a heavenly computer of your own has
become much easier than before. There are three companies
offering microcomputer kits, and the prices of commercial
minicomputers are coming down with every new model.
Not long ago the only way to obtain a computer without paying several thousand
dollars was to buy an old vacuum-tube model, or to go the very difficult route
of building a transistor one from scratch. Even now there is an occasional
vacuum-tube machine available, but the drawbacks are formidable: many are so
large they require a large barn to store, they need a great deal of
air-conditioning and electrical power, and some tubes can be very expensive to
replace. Schematics are needed to get the computer working and maintained, but
they are almost never available. Even with some of the older transistor
computers, updated schematics are usually impossible to obtain. Now and then the
prototype of a recent transistor computer can be bought cheaply, but again,
usually without schematics, so the buyer has two choices: take months or years
to trace out every connection, or rewire most or all of the machine.
As in amateur radio, many computerniks would never think of buying a
ready-built machine; they feel compelled to build one. Up until quite recently,
this task has proved to be so difficult that only a couple of dozen computer
hobbyists in the country had operating digital computers of any real complexity,
and nearly all of them were electronics engineers in the computer industry.
The problem in building a computer from scratch is that so many areas of
specialization are involved: logic, input/output, memory, peripherals, and
mechanical skills such as packaging, back-plane wiring, metal-working, plastics,
and many others.
Although many of the computer hobbyists are engineers who design their own
circuits, most non-engineers must rely on published information, and although
several dozen books and manuals contain computer schematics, they have serious
limitations. A book may show schematics of various portions of a computer -
arithmetic unit, memory, control circuits - but none show how to connect them
together, and anyway, they are usually only partial schematics. Minicomputer
manuals containing schematics can be bought, but many of the parts are
identified only by a manufacturer's code number.
Even supposing an amateur computer-builder did get hold of complete schematics
and all the parts, the one big stumbling block that has thrown many is core
memory, lt's still expensive to buy when new, and when surplus, it may contain
broken cores, or perhaps it became surplus because it couldn't pass the
manufacturer's quality control. Getting
