IBM System/23 Datamaster

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System/23 Datamaster
IBM 5322 - computer.JPG
Release dateJuly 1981; 41 years ago (1981-07)
Introductory priceUS$9,000 (equivalent to $26,825 in 2021)
Discontinued1985 (1985)
Operating systemBASIC built-in
CPUIntel 8085 @ 4.77 MHz
Memory64KB, 128KB, 256 KB RAM
112 KB ROM
StorageTwo 8-inch floppy disk drives
DisplayGreen phosphor CRT display (80 X 24 text)
InputModel F keyboard
Mass95 lb (43 kg)
PredecessorIBM 5120
SuccessorIBM Personal Computer
Related articlesIBM Displaywriter System

The System/23 Datamaster (Model 5322 desktop model and Model 5324 floor model[1]) was announced by IBM in July 1981. The Datamaster was the least expensive IBM computer until the far less expensive and far more popular IBM PC was announced in the following month.[2][3]


IBM Datamaster (2282600489).jpg
Visual differences between 5120 and Datamaster

The Datamaster is an all-in-one computer with text-mode CRT display, keyboard, processor, memory, and two 8-inch floppy disk drives in one cabinet. The processor is an 8-bit Intel 8085[4] running at 4.77 Mhz,[5] with bank switching to manage 256 KB of memory.[6] Available RAM was 64 KB (expandable to 128 KB[5]), and the machine had 6 internal expansion slots.[4] It could display 80 x 24 character text with 256 possible characters, similar to the IBM PC's Code page 437, on a built-in 12" green phosphorous CRT.[4]

The intention of the Datamaster was to provide a computer that could be installed and operated without specialists. A BASIC interpreter was built-in to the system. IBM decided to merge the Datamaster's BASIC implementation with System/34 BASIC, which reportedly delayed the Datamaster by almost a year.[6] When introduced, a single-screen Datamaster sold for around US$9,000 (equivalent to $26,825 in 2021). A second keyboard and screen could be attached in an extended configuration.

Influence on later IBM systems[edit]

The familiarity the design group gained on the Datamaster project encouraged selection of an Intel CPU for the IBM PC. The delay caused by the decision to reuse System/34 BASIC in the Datamaster was one of the factors in IBM's selection of Microsoft BASIC for the PC (the other being the ubiquity of Microsoft BASIC on other home computers at the time).[6]

A number of hardware components from the Datamaster were reused in the later IBM PC. The PC's expansion bus, later known as the ISA bus, was based on the Datamaster's I/O bus.[7] The Datamaster's Model F keyboard with its 5251-style key arrangement was also reused in the PC, albeit with a serial interface (instead of the parallel one used on the Datamaster) and a new external housing.[6]

From a software perspective, since the new IBM PC was using 8-bit characters, there were 128 new characters beyond the 7-bit ASCII characters which could be used. ASCII only defined the characters with numbers from 0 through 127, so the numbers from 128 to 255, which had the high bit turned on, were not defined yet. IBM’s design put serious characters there—three columns of foreign characters, based on their Datamaster experience, as described at Code page 437.


  1. ^ Data Communication Concepts (PDF) (GC21-5169-4 ed.). International Business Machines. September 1983. p. 6-7. Retrieved 7 January 2018.
  2. ^ Pollack, Andrew (1981-08-13). "Big I.B.M.'s Little Computer". The New York Times. p. D1. ISSN 0362-4331. Retrieved 2020-03-16.
  3. ^ Pollack, Andrew (1983-03-27). "Big I.B.M. Has Done It Again". The New York Times. p. Section 3, Page 1. ISSN 0362-4331. Retrieved 2020-03-16.
  4. ^ a b c "IBM 5322 System/32 Datamaster computer".
  5. ^ a b "IBM System/23 Datamaster".
  6. ^ a b c d Bradley, David J. (September 1990). "The Creation of the IBM PC". BYTE. pp. 414–420. Retrieved 2 April 2016.
  7. ^ John Titus (2001-09-15). "Whence Came the IBM PC". Retrieved 2020-10-13.

External links[edit]

IBM personal computers
Preceded by IBM System/23 Succeeded by