Hardware Reference
In-Depth Information
related to the IBM System/23 DataMaster, an office computer system introduced in 1980. In fact,
many of the engineers who developed the IBM PC had originally worked on the DataMaster.
In 1976, a new company called Apple Computer introduced the Apple I, which originally sold for
$666.66. The selling price was an arbitrary number selected by one of Apple's cofounders, Steve
Jobs. This system consisted of a main circuit board screwed to a piece of plywood; a case and power
supply were not included. Only a few of these computers were made, and they reportedly have sold to
collectors for more than $20,000. The Apple II, introduced in 1977, helped set the standard for nearly
all the important microcomputers to follow, including the IBM PC.
The microcomputer world was dominated in 1980 by two types of computer systems. One type, the
Apple II, claimed a large following of loyal users and a gigantic software base that was growing at a
fantastic rate. The other type, CP/M systems, consisted not of a single system but of all the many
systems that evolved from the original MITS Altair. These systems were compatible with one another
and were distinguished by their use of the CP/M OS and expansion slots, which followed the S-100
standard. All these systems were built by a variety of companies and sold under various names. For
the most part, however, these systems used the same software and plug-in hardware. It is interesting
to note that none of these systems was PC compatible or Macintosh compatible, the two primary
standards in place today.
A new competitor looming on the horizon was able to see that to be successful, a personal computer
needed to have an open architecture, slots for expansion, a modular design, and healthy support from
both hardware and software companies other than the original manufacturer of the system. This
competitor turned out to be IBM, which was quite surprising at the time because IBM was not known
for systems with these open-architecture attributes. IBM, in essence, became more like the early
Apple, whereas Apple became like everybody expected IBM to be. The open architecture of the
forthcoming IBM PC and the closed architecture of the forthcoming Macintosh caused a complete
turnaround in the industry.
The IBM Personal Computer
At the end of 1980, IBM decided to truly compete in the rapidly growing low-cost personal computer
market. The company established the Entry Systems Division, located in Boca Raton, Florida, to
develop the new system. The division was intentionally located far away from IBM's main
headquarters in New York, or any other IBM facilities, so that it would be able to operate
independently as a separate unit. This small group consisted of 12 engineers and designers under the
direction of Don Estridge and was charged with developing IBM's first real PC. (IBM considered the
previous 5100 system, developed in 1975, to be an intelligent programmable terminal rather than a
genuine computer, even though it truly was a computer.) Nearly all these engineers had come to the
new division from the System/23 DataMaster project, which was a small office computer system
introduced in 1980 and the direct predecessor of the IBM PC.
Much of the PC's design was influenced by the DataMaster design. In the DataMaster's single-piece
design, the display and keyboard were integrated into the unit. Because these features were limiting,
they became external units on the PC, although the PC keyboard layout and electrical designs were
copied from the DataMaster.
Several other parts of the IBM PC system also were copied from the DataMaster, including the
expansion bus (or input/output slots), which included not only the same physical 62-pin connector, but
also almost identical pin specifications. This copying of the bus design was possible because the PC
