IBM Personal Computer XT

IBM Personal Computer XT

Also known as	IBM XT, PC/XT, XT
Manufacturer	IBM
Type	Personal computer
Release date	March 8, 1983; 41 years ago (1983-03-08)
Discontinued	April 1987 (1987-04)
Operating system	IBM BASIC / PC DOS 2.0-3.20 / PC/IX / SCO Xenix
CPU	Intel 8088 @ 4.77 MHz
Memory	128 KB – 640 KB
Storage	10–20 MB hard drive
Graphics	MDA, CGA
Sound	PC speaker 1-channel square-wave/1-bit digital (PWM-capable)
Power	120/240 VAC
Dimensions	W: 19.5 in (50 cm) H: 5.5 in (14 cm) D: 16 in (41 cm)
Mass	32 lb (15 kg)
Predecessor	IBM Personal Computer
Successor	IBM Personal Computer AT (next model) IBM PS/2 Model 30 (direct replacement)
Related	List of IBM Personal Computer models

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.

Name

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

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

Otherwise the specifications are identical to the original PC.

Expansion slots

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

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

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

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

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

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

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]

Clones and competition

The Compaq Portable also came out in March 1983,^[30] and would prove a popular competitor. Sometimes called the "first PC clone"^[31] and first "legal clone",^[32] that distinction may go to another offering: Columbia Data Products' MPC 1600 "Multi Personal Computer", in June 1982. ^[33][34] Other "clones" included the Seequa Chameleon,^[35][36][37] the Hyperion,^[38] Eagle Computer's Eagle 1600 that September^[39] and the Corona PC.^[40] The latter two companies were sued by IBM and settled out of court, agreeing to re-implement their BIOS in a way that did not violate IBM's copyrights.^[41] AT&T, who owned a 25% share of Olivetti, released the AT&T PC 6300 in June 1984, which was a re-branded version of the Olivetti M24. The PC 6300 offered the 16-bit 8086 clocked at a faster 8 MHz speed that was technically superior to IBM's PC XT.

Timeline

Timeline of the IBM Personal Computer v t e
Asterisk (*) denotes a model released in Japan only

See also

• Amiga Sidecar
• PC-based IBM-compatible mainframes#Personal Computer XT/370

References

1. Enterprise, I. D. G. (August 11, 1986). Computerworld. IDG Enterprise.
2. Upgrading and Repairing PCs, 10th Edition (PDF). 1998. p. 1115.
3. "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. "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. Mueller, Scott (1992). Upgrading and Repairing PCs (2nd ed.). Que Books. pp. 59–79. ISBN 0-88022-856-3.
11. 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. 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. 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. Mueller, Scott (1994). Upgrading and Repairing PCs (4th ed.). Que. ISBN 9781565299320 – via the Internet Archive.
19. Staff writer (June 11, 1984). "IBM Slashes PC Prices, Adds Memory; Drops 64KB". Electronic News. 30 (1501). Sage Publications: 24 – via Gale.
20. Sanger, David E. (June 24, 1987). "I.B.M. Optimistic on Newest PC's". The New York Times: D4 – via ProQuest.
21. 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. 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. 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. 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. 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. "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. "Compaq I Portable computer". www.oldcomputers.net. Retrieved May 14, 2021.
31. "First PC Clone Claim". www.modernmechanix.com. Archived from the original on May 14, 2021. Retrieved May 14, 2021.
32. "Compaq puts out First Legal Clone Claim". d. December 22, 2016. Retrieved May 14, 2021.
33. "History of the Microprocessor and the Personal Computer, Part 3". May 8, 2020.
34. Aboard the Columbia, By Bill Machrone, Page 451, June 1983, PC Mag
35. Hardware:Review:Seequa Chameleon, By Russ Adams, Page 132, November 28, 1983, InfoWorld
36. The Chameleon mystery, By David Needle, Page 5, January 31, 1983, InfoWorld
37. Review Responses: Seequa, By John Schaefer, Page 66, January 30, 1984, InfoWorld
38. David Thomas, Knights of the New Technology: The Inside Story of Canada's Computer Elite, Key Porter Books, 1983 ISBN 0-919493-16-5 pp. 172-179
39. Pournelle, Jerry (September 1983). "Eagles, Text Editors, New Compilers, and Much More". BYTE. p. 307. Retrieved May 14, 2021.
40. "Corona advertisement", InfoWorld, p. 50, July 18, 1983, retrieved May 14, 2021
41. EAGLE'S BATTLE FOR SURVIVAL

Notes

• IBM (1983). Personal Computer Hardware Reference Library: Guide to Operations, Personal Computer XT. IBM Part Number 6936831.

External links

• IBM 5160 information at www.minuszerodegrees.net

Photo galleries:

• XT with 256 KB on system board
• XT 286