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IBM Personal Computer XT

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The IBM Personal Computer XT (model 5160, often shortened to PC/XT) is the second computer in the IBM Personal Computer line, released on March 8, 1983.[1] Except for the addition of a built-in hard drive and extra expansion slots, it is very similar to the original IBM PC model 5150 from 1981.

IBM Personal Computer XT
Also known asIBM XT, PC/XT, XT
ManufacturerIBM
TypePersonal computer
Release dateMarch 8, 1983; 41 years ago (1983-03-08)
DiscontinuedApril 1987 (1987-04)
Operating systemIBM BASIC / PC DOS 2.0-3.20 / PC/IX / SCO Xenix
CPUIntel 8088 @ 4.77 MHz
Memory128 KB – 640 KB
Storage10–20 MB hard drive
GraphicsMDA, CGA
SoundPC speaker 1-channel square-wave/1-bit digital (PWM-capable)
Power120/240 VAC
DimensionsW: 19.5 in (50 cm)
H: 5.5 in (14 cm)
D: 16 in (41 cm)
Mass32 lb (15 kg)
PredecessorIBM Personal Computer
Successor
RelatedList of IBM Personal Computer models

Name

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IBM did not specify an expanded form of "XT" on the machine, press releases, brochures or documentation, but some publications expanded the term as "eXtended Technology" or just "eXTended".[2]

Features

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The XT was regarded as an incremental improvement over the PC and a disappointment compared to the next-generation successor that some had anticipated. Compared to the original IBM PC, the XT has the following major differences:[3]

  • The number of expansion slots was increased from five to eight
  • Base RAM was increased to at least 128 KB
  • 2x32KB ROM ICs replace the previous 5x8KB ROM ICs
  • A 10 MB hard drive was included as standard equipment, with a disk controller featuring Xebec ICs[4]: 111 
  • PC DOS 2.0 was included
  • The 5-pin DIN for the cassette interface was removed

Otherwise the specifications are identical to the original PC.

Expansion slots

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The number of expansion slots in the original IBM PC was a limiting factor for the product, since essential components (such as the video controller, disk controller and printer interface) each came as separate expansion cards and could quickly fill up all five available slots, requiring the user to swap cards in and out as tasks demanded.[5] Some PC clones addressed this problem by integrating components into the motherboard to free up slots,[6] while peripheral manufacturers produced products which integrated multiple functions into one card.[7][8]

The XT addressed the problem by adding three extra expansion slots for a total of eight. While the slots themselves are identical to those in the original PC, the amount of physical space in the chassis differs, so two of the new slots (located behind the hard drive) cannot accept full-length cards. In addition, the spacing of the slots is narrower than in the original PC, making it impossible to install some multi-board cards.[3][8]

Expansion unit

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The 5161 is an expansion chassis using an identical case and power supply to the XT, but instead of a system board, provides a backplane with eight card slots. It connects to the main system unit using an Extender Card in the system unit and a Receiver Card in the Expansion Unit, connected by a custom cable.[3] The 5161 shipped with a 10 MB hard drive, and had room for a second one.[8]

The Expansion Unit can also contain extra memory, but the Extender card inserts wait states for memory in the Expansion Unit, so it may be preferable to install memory into the main system unit.

The 5161 can be connected to either an XT or to the earlier 5150 (the original IBM PC).[9]

Other features

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PC DOS 2.0 offers a 9-sector floppy disk format, providing 180K/360K (single- vs. dual-sided) capacity per disk, compared to the 160K/320K provided by the 8-sector format of previous releases.[3]

The XT was not offered in a floppy-only model for its first two years on the market, although the standard ribbon cable with two floppy connectors was still included. At that time, in order to get a second floppy drive, the user had to purchase the 5161 expansion chassis.[8]

Like the original PC, the XT came with IBM BASIC in ROM. The XT BIOS also displays a memory count during the POST, unlike the original PC.

The XT has a desktop case similar to that of the IBM PC. It weighs 32 pounds (15 kg) and is approximately 19.5 inches (50 cm) wide by 16 inches (41 cm) deep by 5.5 inches (14 cm) high.

Similarly to the original IBM PC, the XT main board included a socket for the Intel 8087 floating point arithmetic coprocessor. This optional chip, when installed, greatly accelerated arithmetic for such applications as computer aided design or other software that required large amounts of arithmetical calculations. Only software that was especially written to take advantage of the coprocessor would show a significant speedup.[10]

The power supply is 130 watts, an upgrade from the original PC. Those sold in the US were configured for 120 V AC only and could not be used with 240 V mains supplies.[10] XTs with 240 V-compatible power supplies were later sold in international markets. Both were rated at 130 watts.[11]

Revisions and variants

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IBM PC/XT 5160 dual floppy drives with 5153 Color Monitor

IBM made several submodels of the XT.

The 3270 PC, a variant of the XT featuring 3270 terminal emulation, was released in October 1983.

Submodel 068 and 078, released in 1985, offered dual-floppy configurations without a hard drive as well, and the new Enhanced Graphics Adapter and Professional Graphics Adapter became available as video card options.[10]

In 1986, the 256–640 KB motherboard models were launched, which switched to half-height drives.

Submodels 268, 278 and 089 came with 101-key keyboards (essentially the IBM Model M, but in a modified variant that used the XT's keyboard protocol and lacked LEDs).

Submodels 267, 277 and 088 had the original keyboard, but 3.5" floppy drives became available and 20MB Seagate ST-225 hard disks in 5.25" half-height size replaced the full-height 10 MB drives.

Submodel 788 was the only XT sold with the Color Graphics Adapter as a standard feature.[11]

Submodels 568, 588, and 589 were used as basis for the XT/370; they had an additional (co-)processor board that could execute System/370 instructions.[11] An XT-based machine with a Series/1 co-processor board existed as well, but it had its own System Unit number, the IBM 4950.[12]

XT 286

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XT 286 badge 
XT 286 badge

In 1986, the XT 286 (model 5162) was released with a 6 MHz Intel 80286 processor. Despite being marketed as a lower-tier model than the IBM AT, this system runs many applications faster than the ATs of the time with 6 MHz 286 processors, since it has zero-wait state RAM.[10]: 95 

It shipped with 640 KB RAM standard, an AT-style 1.2 MB high-density diskette drive and a 20 MB hard disk.[13][14] Despite these features, reviews rated it as a poor market value.[15]

The XT 286 uses a 157-watt power supply, which can internally switch between 115 or 230 V AC operation.[13]

Both the original XT and the XT/286 was discontinued in late 1987 after the launch of the IBM Personal System/2 (PS/2) line. The 8086-powered IBM PS/2 Model 30 served as the direct replacement for the XT in that PS/2 line. Unlike higher-end entries in the PS/2 line, which feature the Micro Channel expansion bus, the Model 30 contains 8-bit ISA bus slots, exactly like the XT.

Comparison table

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See also: List of IBM Personal Computer models
IBM Personal Computer XT models
Type IBM P/N Date announced Date withdrawn Bus No. of
slots 		No. of
bays 		Processor Clock
speed
(MHz) 		Stock onboard RAM
(KB) 		Maximum onboard RAM
(KB) 		FDD HDD Notes Ref(s).
XT 5160-087 March 1983 June 1984 ISA, 8-bit 8 2 Intel 8088 4.77 128 KB 640 KB 360 KB 10 MB   [16]: 236 [17][18]: 1068 
XT 5160-086 June 1984 June 1987 ISA, 8-bit 8 2 Intel 8088 4.77 256 KB 640 KB 360 KB 10 MB   [16]: 236 [19][20][21]
XT 5160-068 April 1985 June 1987 ISA, 8-bit 8 2 Intel 8088 4.77 256 KB 640 KB 360 KB none   [16]: 236 [18]: 1068 [22][20][21]
XT 5160-078 April 1985 June 1987 ISA, 8-bit 8 2 Intel 8088 4.77 256 KB 640 KB two 360 KB none   [16]: 236 [18]: 1068 [22][20][21]
XT 5160-088 April 1986 June 1987 ISA, 8-bit 8 2 Intel 8088 4.77 512 KB 640 KB 360 KB 20 MB Shipped with original IBM PC "Model F" keyboard [16]: 236 [23][20][21]
XT 5160-089 April 1986 June 1987 ISA, 8-bit 8 2 Intel 8088 4.77 512 KB 640 KB 360 KB 20 MB Shipped with Enhanced Keyboard [16]: 236 [23][20][21]
XT 5160-267 April 1986 June 1987 ISA, 8-bit 8 2 Intel 8088 4.77 256 KB 640 KB 360 KB none Shipped with original IBM PC "Model F" keyboard [16]: 236 [23][20][21]
XT 5160-268 April 1986 June 1987 ISA, 8-bit 8 2 Intel 8088 4.77 256 KB 640 KB 360 KB none Shipped with Enhanced Keyboard [16]: 236 [23]
XT 5160-277 April 1986 June 1987 ISA, 8-bit 8 2 Intel 8088 4.77 256 KB 640 KB two 360 KB none Shipped with original IBM PC "Model F" keyboard [23]
XT 5160-278 April 1986 June 1987 ISA, 8-bit 8 2 Intel 8088 4.77 256 KB 640 KB two 360 KB none Shipped with Enhanced Keyboard [16]: 236 [23]
3270 PC 5271-000 Un­known July 1987 ISA, 8-bit 8 2 Intel 8088 4.77 256 KB 640 KB 360 KB none Without printer adapter, fixed disk adapter, and keyboard [24][25]
3270 PC 5271-002 October 1983 July 1987 ISA, 8-bit 8 2 Intel 8088 4.77 256 KB 640 KB 360 KB none Without printer adapter and fixed disk adapter [16]: 49 [19][26]: 10 [25]
3270 PC 5271-004 October 1983 July 1987 ISA, 8-bit 8 2 Intel 8088 4.77 320 KB 640 KB 360 KB none Without fixed disk adapter; stock onboard RAM increased to 384 KB in June 1984 [16]: 49 [19][26]: 10 [25]
3270 PC 5271-006 October 1983 July 1987 ISA, 8-bit 8 2 Intel 8088 4.77 320 KB 640 KB 360 KB 10 MB With fixed disk adapter; stock onboard RAM increased to 384 KB in June 1984 [16]: 49 [19][26]: 10 [25]
XT/370 5160-568 October 1984 April 1987 ISA, 8-bit 8 2 Intel 8088 4.77 256 KB 640 KB 360 KB none [16]: 236 [26][27]
XT/370 5160-588 October 1984 April 1987 ISA, 8-bit 8 2 Intel 8088 4.77 256 KB 640 KB 360 KB 10 MB [16]: 236 [26][27]
XT/370 5160-589 October 1984 April 1987 ISA, 8-bit 8 2 Intel 8088 4.77 256 KB 640 KB 360 KB 10 MB [16]: 236 [27]
XT Model 286 5162-286 September 1986 October 1987 ISA, 16-bit 8 2 Intel 80286 6 640 KB 640 KB 1.2 MB 20 MB   [16]: 48 [28][21]

Reception

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The XT was well received, although PC DOS 2.0 was regarded as a greater improvement than any of the hardware changes, and by the end of 1983 IBM was selling every unit they made.[29] By 1985 the IBM PC AT made the XT obsolete for most customers.[30]

Timeline

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Timeline of the IBM Personal Computer
IBM ThinkCentreIBM NetVistaIBM Palm Top PC 110IBM PC SeriesIBM AptivaIBM PS/ValuePointThinkPadEduQuestIBM PS/noteAmbra Computer CorporationIBM PCradioIBM PS/1IBM PS/55IBM PS/2IBM Personal Computer XT 286IBM PC ConvertibleIBM JXIBM Personal Computer AT/370IBM Personal Computer ATIBM Industrial ComputerIBM PCjrIBM Portable Personal ComputerIBM Personal Computer XT/370IBM 3270 PCIBM Personal Computer XTIBM 5550IBM Personal ComputerIBM System/23 DatamasterIBM 5120IBM 5110IBM 5100
Asterisk (*) denotes a model released in Japan only

See also

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References

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  1. ^ Enterprise, I. D. G. (August 11, 1986). Computerworld. IDG Enterprise.
  2. ^ Upgrading and Repairing PCs, 10th Edition (PDF). 1998. p. 1115.
  3. ^ a b c d "IBM Unveils Top-of-the-Line Personal Computer". Byte. Vol. 8, no. 5. May 1983. p. 520.
  4. ^ Barkow, Tim (October 1996). "The Bottom Feeders". Wired. Vol. 4, no. 10. Wired Ventures. pp. 110–127. Archived from the original on November 12, 2015.
  5. ^ Dievendorff, Dick (1981). IBM Personal Computer Questions and Answers. IBM. pp. 9–10.
  6. ^ Freeze, Ken (December 16, 1985). "Leading Edge: Superior Value In IBM-PC Clone Market Contest". InfoWorld. p. 43. Retrieved July 22, 2014.
  7. ^ Inc, InfoWorld Media Group (November 14, 1983). InfoWorld. InfoWorld Media Group, Inc. {{cite book}}: |last= has generic name (help)
  8. ^ a b c d "Inside the IBM PC". Byte. Vol. 8, no. 11. November 1983.
  9. ^ Personal Computer Family Service Information Manual (January 1989), IBM document SA38-0037-00, pages 7-1 to 7-3
  10. ^ a b c d Mueller, Scott (1992). Upgrading and Repairing PCs (2nd ed.). Que Books. pp. 59–79. ISBN 0-88022-856-3.
  11. ^ a b c Personal Computer Family Service Information Manual (January 1989), IBM document SA38-0037-00, page 6-2
  12. ^ Personal Computer Family Service Information Manual (January 1989), IBM document SA38-0037-00, page 14-1
  13. ^ a b Personal Computer Family Service Information Manual (January 1989), IBM document SA38-0037-00, pages 8-1 to 8-2
  14. ^ "The AT Clone from IBM", PC Magazine, January 13, 1987
  15. ^ InfoWorld Media Group, Inc. (March 23, 1987). InfoWorld. InfoWorld Media Group, Inc. pp. 49. ISSN 0199-6649.
  16. ^ a b c d e f g h i j k l m n o p IBM Personal System/2 and IBM Personal Computer Product Reference (PDF) (4.0 ed.). International Business Machines Corporation. April 6, 1987 – via Bitsavers.
  17. ^ Sandler, Corey (April 1983). "IBM Drops the First Shoe". PC Magazine. 1 (12). Ziff-Davis: 90–102 – via Google Books.
  18. ^ a b c Mueller, Scott (1994). Upgrading and Repairing PCs (4th ed.). Que. ISBN 9781565299320 – via the Internet Archive.
  19. ^ a b c d Staff writer (June 11, 1984). "IBM Slashes PC Prices, Adds Memory; Drops 64KB". Electronic News. 30 (1501). Sage Publications: 24 – via Gale.
  20. ^ a b c d e f Sanger, David E. (June 24, 1987). "I.B.M. Optimistic on Newest PC's". The New York Times: D4 – via ProQuest.
  21. ^ a b c d e f g Bridges, Linda; Laura Brennan; Jim Forbes; Bruce Stephen (July 7, 1987). "PC managers regrouping after XT, AT closeout". PC Week. 4 (27). Ziff-Davis: 4 – via Gale. IBM's recent announcement that it will formally discontinue its PC XT line and eventually phase out its PC AT came as no surprise to many corporate users. [...] William Lowe, president of IBM's Entry Systems Division in Boca Raton, Fla., told Wall Street analysts on June 30 that the only remaining XT, the XT 286, will be discontinued within three months and that IBM is working with dealers and large accounts to determine how many more ATs it will make to fill orders.
  22. ^ a b Sager, Ira (April 8, 1985). "IBM moves to reduce PC XT inventories". Electronic News. 31. Sage Publications: 24 et seq – via Gale. The new floppy disk-based versions of the PC XT basically just strips the 10MB hard disk from the earlier unit. The machines come with base memory of 256KB and are available in either single or dual 360 KB diskette versions. A single diskette unit with keyboard and 256 KB of main memory is priced at $2,270, while the dual diskette version is priced at $2,570. A fully configured PC XT with 256 KB of RAM, a 360 KB diskette, keyboard, monochrome monitor and adapter, and operating system comes in at about $2,860.
  23. ^ a b c d e f Whitmore, Sam (April 8, 1986). "Product blitz may signal more aggressive IBM: firm ups ante for the makers of compatibles". PC Week. 3 (14). Ziff-Davis: 1 – via Gale.
  24. ^ "IBM 3770 Family Batch Communications Terminals" (PDF). Distributed Processing & Intelligent Tennlnals. Datapro: C21-491-101. January 1984 – via Bitsavers.org.
  25. ^ a b c d Libes, Sol (February 28, 1984). "3270 emulation board makers, beware! IBM is aiming at you". PC Week. 1 (28). Ziff-Davis: 25 et seq – via Gale.
  26. ^ a b c d e Henkel, T. (October 24, 1983). "IBM Takes Wraps off Two Micros Capable of Accessing Mainframes". Computerworld. 17 (43). IDG Publications: 1, 10 – via Google Books.
  27. ^ a b c "IBM Gives Up on the Personal XT/, AT/370". Computer Business Review. New Statesman Media Group. April 13, 1987. Archived from the original on September 20, 2023.
  28. ^ Ristelhueber, Robert; Ira Sager (September 8, 1986). "4 PC suppliers add 286 units in battle with compatibles". Electronic News. 32. Sage Publications: 1 et seq – via Gale.
  29. ^ Archer, Rowland Jr. (November 1983). "The IBM PC XT and DOS 2.00". BYTE. pp. 294–304. Retrieved May 14, 2021.
  30. ^ Pournelle, Jerry (January 1985). "The Fast Lane". BYTE. p. 363. Retrieved October 4, 2024.
Notes
  • IBM (1983). Personal Computer Hardware Reference Library: Guide to Operations, Personal Computer XT. IBM Part Number 6936831.
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