control electronics onto the drive itself
to lower costs, improve performance,
and supported much larger drive sizes.
Drive manufacturers cooperated with
motherboard producers (and the producers of chipset and BIOS components who supplied them), computer
assemblers, and of course Microsoft to
incorporate the necessary changes. Another big change was the introduction
of several rival higher speed bus standards (EISA, PCI, and VLB), all of which
required motherboard and expansion
card producers to adopt new technology but preserved the physical dimensions of the card itself.
The most difficult thing to change
was what would, in a more conventional kind of high-technology product,
have been the easiest: the case design.
The standard power supply occupied
the right rear corner, with an inconveniently located switch. The case and
the motherboard would invariably
be produced by different companies.
This was not a problem, as long as
the motherboard was not too large for
the case and had its mounting holes
in the right places. It could shrink
a little, but not too much as it had to
reach the mounting holes and extend
far enough to align its expansion slots
and keyboard connector correctly with
the cutouts in the back of the case.
This determined the minimum width
of the case and the height was set by
the height of the expansion cards, so
PCs remained bulky even as workstations shrank into fashionable “pizza
boxes.” Any use of custom components raised costs and limited flexibility, though cases did eventually start
to feature power switches on the front
and special rear mountings for mouse
and printer sockets. Even the popular
“mini-tower” format just took the traditional desktop layout, shortened it,
and turned it sideways.
Tiny choices made by the original
PC/AT designers imposed fundamental
constraints 10 years later. For example,
graphics, network, and sound control-
lers were rarely integrated onto the
motherboard. Why? Not because of any
technological limit, but simply because
there were no holes on the back of
the standard case through which they
could protrude to the outside world. On
the other hand, hard and floppy disk
controllers were widely integrated by
this point as the standard connector
could simply be routed inside the case
to the motherboard.
The history of technology includes
many landmark products and many
successful standards. However, the IBM
PC is perhaps unique in evolving seam-
lessly from a single proprietary product
to an open standard and the foundation
of an entire global industry. Some ideas
developed by historians are useful in
understanding this—for example, the
idea of backward compatibility long
predates the computer, as historian
Thomas Hughes showed when he cre-
ated the term “technological momen-
tum” to describe the power of estab-
lished electrical power systems. 1 The
special characteristics of computer
systems, in particular the rapid growth
in power, the layering of technologies,
and the use of emulation to retain com-
patibility have given the PC a new kind
of evolutionary flexibility.
The creation of the original PC is told from
an IBM perspective in Chposky, J. and
Leonsis, T. Blue Magic: The People, Power,
and Politics Behind the IBM Personal
Computer. Facts on File, n Y, 1988.
For a broader and more entertaining look
on the early years of the personal computer
industry, including insightful analysis of
the rise of the clone industry, see Cringely,
R. X. Accidental Empires: How the Boys of
Silicon Valley Make their Millions, Battle
Foreign Competition, and Still Can’t Get a
Date. Addison-Wesley, Reading, MA, 1992.
historians have started to think about
the rise of the PC as a standard in Sumner,
J. “Standard and Compatibility: The Rise
of the PC Computing Platform.” In
“By whose standards? Standardization,
stability and uniformity in the history of
information and electrical technologies.”
Volume 28 of History of Technology,
J. Sumner and G.J.n. Gooday, Eds.,
Continuum, London, 2008, 101–127.
1. hughes, t. Networks of Power: Electrification
in Western Society, 1880–1930. johns hopkins
university Press, baltimore, Md, 1983.
2. knobelsdorff, k.e. IbM’s four-month-old Ps/2 has put
computer world on hold. Christian Science Monitor
(aug. 19, 1987).
3. Mackenzie, d. Material Markets: How Economic Agents
are Constructed. oxford university Press, ny, 2009.
4. Pinch, t. and swedberg, r. eds., Living in a Material
World. MIt Press, Cambridge, Ma, 2008.
5. sanger, d.e. IbM offers a blitz of new PC’s. New York
Times (apr. 3, 1987).
Thomas haigh ( firstname.lastname@example.org) is an associate
professor of information studies at the university of
wisconsin, Milwaukee and chair of the sIgCIs group for
historians of computing.