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IBM PS/2 Model 55 SX

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Personal System/2 Model 55 SX
A PS/2 Model 55 SX
DeveloperInternational Business Machines Corporation (IBM)
ManufacturerIBM
Product familyPersonal System/2
TypePersonal computer
Release dateMay 1989 (1989-05)
Lifespan1989–1992
DiscontinuedMay 1992 (1992-05)
Units soldOver 1 million
Media1.44 MB 3.5-in floppy disks
CPUIntel 386SX at 16 MHz
Storage30–80 MB hard drive
GraphicsVideo Graphics Array
Power120/240 VAC ～
RelatedList of IBM PS/2 models

The Personal System/2 Model 55 SX is a midrange desktop computer in IBM's Personal System/2 (PS/2) family of personal computers. First released in May 1989, the Model 55 SX features an Intel 386SX processor running at a clock speed of 16 MHz. In October 1990, IBM introduced a diskless workstation version of the Model 55 SX, called the Personal System/2 Model 55 LS. The Model 55 SX was the best-ever selling computer in the PS/2 range, accounting for 23 percent of IBM's PC sales within four months of its introduction. By 1991, the PS/2 Model 55 SX was the best-selling x86-based PC in the world.[1]

Development and release

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IBM announced the PS/2 Model 55 SX in May 1989, alongside the portable PS/2 Model P70. The Model 55 SX was IBM's first personal computer to use the 386SX processor by Intel, released almost a year earlier in June 1988.[2][3] The 386SX was a cost-reduced version of the 32-bit 386 processor, also by Intel. Internally, the i386SX supports 32-bit operations, but its data bus could only access RAM 16 bits at a time, leading to a performance reduction of around 30 percent compared to a 386 processor with the same clock speed.[3] The PS/2 Model 55 SX sports a horizontal desktop case exactly identical to that of the PS/2 Model 30, released earlier in 1987.[2]

The Model 55 SX, along with the Model P70, were the first new models of PS/2 to be assembled from the beginning at IBM's factory in Raleigh, North Carolina. Previously, models of PS/2 were manufactured at IBM's facility in Boca Raton, Florida, before the company moved personal computer production to Raleigh in 1989. Prototyping of the computers were still performed in Boca Raton, however.[4] Owing to initial runs of the 55 SX's motherboard failing to meet IBM's quality-control standards, announcement of the computer was delayed by over a month, according to InfoWorld, pending motherboard design revisions.[5]: 1 

Specifications

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Internal view of the Model 55 SX, detailing the three 16-bit Micro Channel expansion slots

Model 55 SX

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All models of the Model 55 SX features a 386SX processor clocked at 16 MHz and have 2 MB of RAM stock and on-board VGA graphics.[2][6][7] As a consequence of the processor's 16-bit data path, the Model 55 SX sports only three 16-bit Micro Channel expansion slots, whereas other true 32-bit offerings in the PS/2 line carried at least some 32-bit slots.[2] One of the Model 55 SX's 16-bit slots features an extension for specific MCA graphics adapters such as the 8514/A.[8]: 36  The initial two models in the PS/2 Model 55 SX range were the Model 55 SX-031, featuring a 30-MB hard disk drive, and the Model 55 SX-061, featuring a 60-MB hard drive.[2] In June 1991, IBM introduced two more models of Model 55 SX, with 40- and 80-MB drives (the Model 55 SX-041 and Model 55 SX-081, respectively).[7] All hard drives were of Enhanced Small Disk Interface (ESDI) specification, which IBM used extensively in the PS/2 range and which was faster than the ST-506 interface of older IBM PCs.[9] The computer has two 3.5-inch drive bays, both occupied as stock by the included hard drives and the 3.5-inch floppy disk drives. Users had to make use of external drives if they wanted more storage options, with the associated controllers taking up one of the three Micro Channel slots.[10]

Model 55 LS

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In October 1990, IBM introduced the Model 55 LS (LAN Station), which were diskless-workstation versions of the Model 55 SX featuring no installed drives—not even a floppy drive. Instead, the computers came preinstalled with either an Ethernet adapter or a Token Ring adapter (IBM's own networking standard), with the machines booting their operating system from a LAN server and having all applications and date remotely served and saved. IBM had been offering the Model 55 LS as a special bid version of the Model 55 SX for customers who specifically requested since its release in 1989, but the Model 55 LS was IBM's first computer specifically branded as a diskless workstation.[6]

Sales

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Sales of the Model 55 SX ramped up significantly over the summer of 1989, with the machine representing 23 percent of all IBM personal computers sold by September 1989, up from 4 percent only two months earlier.[11] This share of IBM's PC sales remained steady into the next year, the Model 55 SX representing 22 percent of IBM's PC sales in June 1990.[12] For the majority of 1990, it was the best-selling personal computer in the United States.[13] By 1991, it was the best selling x86-based PC globally.[1] It was IBM's best-selling PS/2 by a significant margin, with the company selling 25,000 units of the computer in August 1990 alone.[6] The heretofore best-selling PS/2 Model 50 Z, meanwhile, sold only 18,000 in a single month (October 1988).[14] This represented a reversal of fortunes for the PS/2 line, which had underperformed as a whole compared to IBM's earlier PC line.[1] The Model 55 SX proved so popular that IBM reported parts shortages in April 1990.[15]

Apple Computer eventually overtook IBM for the number one spot in U.S. computer sales with the Macintosh Classic in June 1991.[16] However, it retained its status as the best-selling PC-compatible for the remainder of 1991 and the first half of 1992.[1][17][18] IBM officially withdrew the PS/2 Model 55 SX in May 1992, replacing it with the similarly specced PS/2 Models 56 and 57.[19]

Reception

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Despite its massive sales success, the Model 55 SX received mixed, generally negative, reviews in the press. Despite earning an Editors' Choice Awards in PC Magazine in 1990,[20] the magazine's Tom Unger had earlier wrote that, "Even with the loaded motherboard, some users may feel constrained by getting just three expansion slots", praising the solid construction and motherboard integration while panning the hard drives for being slow.[10]: 136  InfoWorld's Eugene Wong called the Model 55 SX slower than most other 16-MHz 386SX machines despite being significantly more expensive.[21] Russ Lockwood of Personal Computing found it the slowest of four 386SX machines reviewed and wrote that the Micro Channel architecture's potential for bus mastering was wasted on the drive controller and on-board graphics which were not capable of such. However, unlike Wong, he praised the motherboard's construction and called it price-competitive.[22] In a review of several 386SX machines, PC World's T. J. Byers put it at the bottom of the list owing to its slow performance and limited potential for expansion.[23]

Submodels

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See also: List of IBM PS/2 models
IBM PS/2 Model 55 SX submodels
Model IBM P/N Processor Clock speed
(MHz)		 Bus No. of
slots		 No. of
drive bays		 FDD HDD Stock
RAM		 Maximum
RAM		 Video adapter Monitor Form factor Date introduced Notes Ref(s).
55 SX 8555-031 Intel 386SX 16 (0–2 w) MCA, 16-bit 3 2 one 1.44 MB 30 MB (ESDI) 2 MB 8 MB VGA optional Desktop May 1989 [24][25]
55 SX 8555-041 Intel 386SX 16 (0–2 w) MCA, 16-bit 3 2 one 1.44 MB 40 MB (ESDI) 2 MB 8 MB VGA optional Desktop June 1991 [26][25]
55 SX 8555-061 Intel 386SX 16 (0–2 w) MCA, 16-bit 3 2 one 1.44 MB 60 MB (ESDI) 2 MB 8 MB VGA optional Desktop May 1989 [24][25]
55 SX 8555-081 Intel 386SX 16 (0–2 w) MCA, 16-bit 3 2 one 1.44 MB 80 MB (ESDI) 2 MB 8 MB VGA optional Desktop June 1991 [26][25]
55 LS 8555-LE0 Intel 386SX 16 (0–2 w) MCA, 16-bit 3 2 none none 2 MB 8 MB VGA optional Desktop October 1990 [24][6]
55 LS 8555-LT0 Intel 386SX 16 (0–2 w) MCA, 16-bit 3 2 none none 2 MB 8 MB VGA optional Desktop October 1990 [24][6]

References

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  1. ^ a b c d Kalpan, Alan (September 1991). "IBM's counter-clones". PC World. 9 (9). IDG Publications: 105 et seq – via Gale.
  2. ^ a b c d e Helliwell, John (May 15, 1989). "Form outweighs function with IBM's 55 SX, P70". PC Week. 6 (19). Ziff-Davis: 1 et seq – via Gale.
  3. ^ a b Staff writer (June 20, 1988). "Intel develops low-end version of its 386 chip". The Globe and Mail. Bell Globemedia: B9 – via ProQuest.
  4. ^ Associated Press (May 10, 1989). "IBM to Add 2 PC Models to Market". Sun Sentinel: 1D – via ProQuest.
  5. ^ LaPlante, Alice (April 10, 1989). "Quality Woes Nix Model 55 SX Debut". InfoWorld. 11 (15). IDG Publications: 1, 125 – via Google Books.
  6. ^ a b c d e Brennan, Laura (October 15, 1990). "By naming, pricing diskless PC, IBM bolsters LAN lineup". PC Week. 7 (41). Ziff-Davis: 10 – via Gale.
  7. ^ a b Staff writer (June 17, 1991). "New PS/2 386SX models: feature faster performance, greater flexibility at lower prices". EDGE. 2 (56). EDGE Publishing: 6 – via Gale.
  8. ^ Jones, Mitt (July 1989). "IBM Introduces Feature-laden Portable PS/2 Model P70 386, Entry-Level PS/2 Model 55 SX". PC Magazine. 8 (13). Ziff-Davis: 33, 35–36 – via Google Books.
  9. ^ Lavin, Paul (April 11, 1990). "True-blue PS/2". PC User (130). EMAP Media: 103 et seq – via Gale.
  10. ^ a b Unger, Tom (January 30, 1990). "IBM Corp.: IBM PS/2 Model 55SX". PC Magazine. 9 (2). Ziff-Davis: 136–137 – via Google Books.
  11. ^ Anderson, Kate (February 26, 1990). "IBM's share of year-ahead planned micro purchases highest since 1988". PC Week. 7 (8). Ziff-Davis: 138 – via Gale.
  12. ^ Lunan, Charles (June 6, 1990). "IBM Lowers Prices to Fight Off Clones". Sun Sentinel: 3D – via ProQuest.
  13. ^ Lunan, Charles (August 11, 1991). "IBM Seeking New Success After PC: 1991 Shaping Up as a Pivotal Year for Computer Firm". Sun Sentinel: 1D – via ProQuest.
  14. ^ LaPlante, Alice (December 12, 1988). "Survey Shows MCA Products Catching On". InfoWorld. 10 (50). IDG Publications: 5 – via Google Books.
  15. ^ LaPlante, Alice (April 30, 1990). "PS/2 Model 50Z, 55 SX in Short Supply". InfoWorld. 12 (18). IDG Publications: 1, 101 – via Google Books.
  16. ^ Hooper, Laurence (June 6, 1991). "IBM to Unveil 3 New Models for Its PC Line". The Wall Street Journal. Dow Jones & Company: B4 – via ProQuest.
  17. ^ Hildebrand, Carol (January 27, 1992). "IBM to pump up midrange PC line". Computerworld. XXVI (4). IDG Publications: 4 – via Google Books.
  18. ^ Staff writer (May 1992). "Best-Sellers". PC World. 10 (5). IDG Publications: 84 – via the Internet Archive.
  19. ^ Staff writers (February 26, 1992). "Chips That Zip". Sun Sentinel: 3D – via ProQuest.
  20. ^ Ray, Garry (July 1990). "The 386SX blizzard: how to distinguish among the more than 100 machines available". Lotus. 6 (7). Lotus Publishing: 84 et seq – via Gale.
  21. ^ Wong, Eugene (September 4, 1989). "IBM's 55 SX Is Slower Than Most Other 16-MHz PCs". InfoWorld. 11 (36). IDG Publications: 84–85 – via Google Books.
  22. ^ Lockwood, Russ (August 1989). "80386SX Performance Trials". Personal Computing. 13 (8). VNU Business Information Services: 87–98 – via ProQuest.
  23. ^ Byers, T. J. (December 1989). "IBM PS/2 Model 55 SX". PC World. 7 (12). IDG Publications: 124 et seq – via Gale.
  24. ^ a b c d "IBM PS/2 (Model 55 SX/55 LS) – Technical Specifications". International Business Machines Corporation. 2000. Retrieved September 28, 2021 – via Ardent Tool.
  25. ^ a b c d Bowlds, Pat A. (1991). Micro Channel Architecture: Revolution in Personal Computing. Van Nostrand Reinhold. pp. 338–339. ISBN 9780442004330 – via Google Books.
  26. ^ a b Mueller, Scott (1994). Upgrading and Repairing PCs (4th ed.). Que. pp. 1124–1125. ISBN 9781565299320 – via the Internet Archive.
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