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The Bottom Feeders

Oct 1 1996

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 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 on most sub-models, with a disk controller featuring Xebec ICs⁴: 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

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.⁷⁸

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.⁹¹⁰

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.¹¹ The 5161 shipped with a 10 MB hard drive, and had room for a second one.¹²

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).¹³

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.¹⁴

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.¹⁵

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.¹⁶

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.¹⁷ XTs with 240 V-compatible power supplies were later sold in international markets. Both were rated at 130 watts.¹⁸

Revisions and variants

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.¹⁹

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.²⁰

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.²¹ An XT-based machine with a Series/1 co-processor board existed as well, but it had its own System Unit number, the IBM 4950.²²

XT 286

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.²³: 95 

It shipped with 640 KB RAM standard, an AT-style 1.2 MB high-density diskette drive and a 20 MB hard disk.²⁴²⁵ Despite these features, reviews rated it as a poor market value.²⁶

The XT 286 uses a 157-watt power supply, which can internally switch between 115 or 230 V AC operation.²⁷

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

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.⁸⁷ By 1985 the IBM PC AT made the XT obsolete for most customers.⁸⁸

Timeline

See also

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

• 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

References

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2. Upgrading and Repairing PCs, 10th Edition (PDF). 1998. p. 1115. http://ptgmedia.pearsoncmg.com/imprint_downloads/informit/que/upgrading/fourteenth_edition/DVD/PCs10th.pdf ↩

3. "IBM Unveils Top-of-the-Line Personal Computer". Byte. Vol. 8, no. 5. May 1983. p. 520. https://archive.org/details/byte-magazine-1983-05 ↩

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. https://web.archive.org/web/20151112091504/https://www.wired.com/1996/10/es-intaglio/ ↩

5. Dievendorff, Dick (1981). IBM Personal Computer Questions and Answers. IBM. pp. 9–10. http://bitsavers.trailing-edge.com/pdf/ibm/pc/pc/ ↩

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11. "IBM Unveils Top-of-the-Line Personal Computer". Byte. Vol. 8, no. 5. May 1983. p. 520. https://archive.org/details/byte-magazine-1983-05 ↩

12. "Inside the IBM PC". Byte. Vol. 8, no. 11. November 1983. https://archive.org/details/byte-magazine-1983-11 ↩

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14. "IBM Unveils Top-of-the-Line Personal Computer". Byte. Vol. 8, no. 5. May 1983. p. 520. https://archive.org/details/byte-magazine-1983-05 ↩

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21. Personal Computer Family Service Information Manual (January 1989), IBM document SA38-0037-00, page 6-2 ↩

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26. InfoWorld. InfoWorld Media Group, Inc. March 23, 1987. pp. 49. ISSN 0199-6649. https://archive.org/details/bub_gb_yjAEAAAAMBAJ ↩

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28. IBM Personal System/2 and IBM Personal Computer Product Reference (PDF) (4.0 ed.). International Business Machines Corporation. April 6, 1987 – via Bitsavers. https://bitsavers.org/pdf/ibm/pc/PS2_and_IBM_PC_Product_Reference_Version_4.0_Apr87.pdf#page=244 ↩

29. Sandler, Corey (April 1983). "IBM Drops the First Shoe". PC Magazine. 1 (12). Ziff-Davis: 90–102 – via Google Books. https://books.google.com/books?id=7wCiNAUEuAMC&pg=RA2-PA90 ↩

30. Mueller, Scott (1994). Upgrading and Repairing PCs (4th ed.). Que. ISBN 9781565299320 – via the Internet Archive. 9781565299320 ↩

31. IBM Personal System/2 and IBM Personal Computer Product Reference (PDF) (4.0 ed.). International Business Machines Corporation. April 6, 1987 – via Bitsavers. https://bitsavers.org/pdf/ibm/pc/PS2_and_IBM_PC_Product_Reference_Version_4.0_Apr87.pdf#page=244 ↩

32. Staff writer (June 11, 1984). "IBM Slashes PC Prices, Adds Memory; Drops 64KB". Electronic News. 30 (1501). Sage Publications: 24 – via Gale. https://link.gale.com/apps/doc/A554458/GPS?sid=wikipedia ↩

33. Sanger, David E. (June 24, 1987). "I.B.M. Optimistic on Newest PC's". The New York Times: D4 – via ProQuest. https://www.proquest.com/docview/426534977/ ↩

34. 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. https://link.gale.com/apps/doc/A5027977/GPS?sid=wikipedia ↩

35. IBM Personal System/2 and IBM Personal Computer Product Reference (PDF) (4.0 ed.). International Business Machines Corporation. April 6, 1987 – via Bitsavers. https://bitsavers.org/pdf/ibm/pc/PS2_and_IBM_PC_Product_Reference_Version_4.0_Apr87.pdf#page=244 ↩

36. Mueller, Scott (1994). Upgrading and Repairing PCs (4th ed.). Que. ISBN 9781565299320 – via the Internet Archive. 9781565299320 ↩

37. 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. https://link.gale.com/apps/doc/A3723060/GPS?sid=wikipedia ↩

38. Sanger, David E. (June 24, 1987). "I.B.M. Optimistic on Newest PC's". The New York Times: D4 – via ProQuest. https://www.proquest.com/docview/426534977/ ↩

39. 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. https://link.gale.com/apps/doc/A5027977/GPS?sid=wikipedia ↩

40. IBM Personal System/2 and IBM Personal Computer Product Reference (PDF) (4.0 ed.). International Business Machines Corporation. April 6, 1987 – via Bitsavers. https://bitsavers.org/pdf/ibm/pc/PS2_and_IBM_PC_Product_Reference_Version_4.0_Apr87.pdf#page=244 ↩

41. Mueller, Scott (1994). Upgrading and Repairing PCs (4th ed.). Que. ISBN 9781565299320 – via the Internet Archive. 9781565299320 ↩

42. 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. https://link.gale.com/apps/doc/A3723060/GPS?sid=wikipedia ↩

43. Sanger, David E. (June 24, 1987). "I.B.M. Optimistic on Newest PC's". The New York Times: D4 – via ProQuest. https://www.proquest.com/docview/426534977/ ↩

44. 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. https://link.gale.com/apps/doc/A5027977/GPS?sid=wikipedia ↩

45. IBM Personal System/2 and IBM Personal Computer Product Reference (PDF) (4.0 ed.). International Business Machines Corporation. April 6, 1987 – via Bitsavers. https://bitsavers.org/pdf/ibm/pc/PS2_and_IBM_PC_Product_Reference_Version_4.0_Apr87.pdf#page=244 ↩

46. 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. https://link.gale.com/apps/doc/A666904/GPS?sid=wikipedia ↩

47. Sanger, David E. (June 24, 1987). "I.B.M. Optimistic on Newest PC's". The New York Times: D4 – via ProQuest. https://www.proquest.com/docview/426534977/ ↩

48. 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. https://link.gale.com/apps/doc/A5027977/GPS?sid=wikipedia ↩

49. IBM Personal System/2 and IBM Personal Computer Product Reference (PDF) (4.0 ed.). International Business Machines Corporation. April 6, 1987 – via Bitsavers. https://bitsavers.org/pdf/ibm/pc/PS2_and_IBM_PC_Product_Reference_Version_4.0_Apr87.pdf#page=244 ↩

50. 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. https://link.gale.com/apps/doc/A666904/GPS?sid=wikipedia ↩

51. Sanger, David E. (June 24, 1987). "I.B.M. Optimistic on Newest PC's". The New York Times: D4 – via ProQuest. https://www.proquest.com/docview/426534977/ ↩

52. 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. https://link.gale.com/apps/doc/A5027977/GPS?sid=wikipedia ↩

53. IBM Personal System/2 and IBM Personal Computer Product Reference (PDF) (4.0 ed.). International Business Machines Corporation. April 6, 1987 – via Bitsavers. https://bitsavers.org/pdf/ibm/pc/PS2_and_IBM_PC_Product_Reference_Version_4.0_Apr87.pdf#page=244 ↩

54. 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. https://link.gale.com/apps/doc/A666904/GPS?sid=wikipedia ↩

55. Sanger, David E. (June 24, 1987). "I.B.M. Optimistic on Newest PC's". The New York Times: D4 – via ProQuest. https://www.proquest.com/docview/426534977/ ↩

56. 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. https://link.gale.com/apps/doc/A5027977/GPS?sid=wikipedia ↩

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71. 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. https://link.gale.com/apps/doc/A3150465/GPS?sid=wikipedia ↩

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73. Staff writer (June 11, 1984). "IBM Slashes PC Prices, Adds Memory; Drops 64KB". Electronic News. 30 (1501). Sage Publications: 24 – via Gale. https://link.gale.com/apps/doc/A554458/GPS?sid=wikipedia ↩

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75. 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. https://link.gale.com/apps/doc/A3150465/GPS?sid=wikipedia ↩

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77. 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. https://books.google.com/books?id=wFqbDqPhSMcC&pg=PA1 ↩

78. "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. https://archive.today/20230920021426/https://techmonitor.ai/technology/ibm_gives_up_on_the_personal_xt_at370 ↩

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