IBM PS/2 Model 55 SX

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.{{cite journal | last=Helliwell | first=John | date=May 15, 1989 | url=https://link.gale.com/apps/doc/A7256136/GPS?sid=wikipedia | title=Form outweighs function with IBM's 55 SX, P70 | journal=PC Week | publisher=Ziff-Davis | volume=6 | issue=19 | pages=1 et seq | via=Gale}}{{cite journal | last=Staff writer | date=June 20, 1988 | url=https://www.proquest.com/docview/385908263/ | title=Intel develops low-end version of its 386 chip | journal=The Globe and Mail | publisher=Bell Globemedia | page=B9 | via=ProQuest}} 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. 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.

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.{{cite journal | last=((Associated Press)) | date=May 10, 1989 | url=https://www.proquest.com/docview/389288058/ | title=IBM to Add 2 PC Models to Market | journal=Sun Sentinel | page=1D | via=ProQuest}} 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.{{cite journal | last=LaPlante | first=Alice | date=April 10, 1989 | url=https://books.google.com/books?id=GDoEAAAAMBAJ&pg=PA135 | title=Quality Woes Nix Model 55 SX Debut | journal=InfoWorld | publisher=IDG Publications | volume=11 | issue=15 | pages=1, 125 | via=Google Books}}{{rp|1}}

File:IBM PS2 MCA Model 55 SX, slot riser card.jpg expansion slots]]

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.{{cite journal | last=Staff writer | date=June 17, 1991 | url=https://link.gale.com/apps/doc/A10928320/GPS?sid=wikipedia | title=New PS/2 386SX models: feature faster performance, greater flexibility at lower prices | journal=EDGE | publisher=EDGE Publishing | volume=2 | issue=56 | page=6 | via=Gale}} 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. One of the Model 55 SX's 16-bit slots features an extension for specific MCA graphics adapters such as the 8514/A.{{cite journal | last=Jones | first=Mitt | date=July 1989 | url=https://books.google.com/books?id=CbsaONN5y1IC&pg=PP38 | title=IBM Introduces Feature-laden Portable PS/2 Model P70 386, Entry-Level PS/2 Model 55 SX | journal=PC Magazine | publisher=Ziff-Davis | volume=8 | issue=13 | page=33, 35–36 | via=Google Books}}{{rp|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. 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). 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.{{cite journal | last=Lavin | first=Paul | date=April 11, 1990 | url=https://link.gale.com/apps/doc/A8419960/GPS?sid=wikipedia | title=True-blue PS/2 | journal=PC User | publisher=EMAP Media | issue=130 | pages=103 et seq | via=Gale}} 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.{{cite journal | last=Unger | first=Tom | date=January 30, 1990 | url=https://books.google.com/books?id=ySO4VbD0-mcC&pg=PT139 | title=IBM Corp.: IBM PS/2 Model 55SX | journal=PC Magazine | publisher=Ziff-Davis | volume=9 | issue=2 | pages=136–137 | via=Google Books}}

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.

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.{{cite journal | last=Anderson | first=Kate | date=February 26, 1990 | url=https://link.gale.com/apps/doc/A8182786/GPS?sid=wikipedia | title=IBM's share of year-ahead planned micro purchases highest since 1988 | journal=PC Week | publisher=Ziff-Davis | volume=7 | issue=8 | page=138 | via=Gale}} 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.{{cite journal | last=Lunan | first=Charles | date=June 6, 1990 | url=https://www.proquest.com/docview/389196716/ | title=IBM Lowers Prices to Fight Off Clones | journal=Sun Sentinel | page=3D | via=ProQuest}} For the majority of 1990, it was the best-selling personal computer in the United States.{{cite journal | last=Lunan | first=Charles | date=August 11, 1991 | url=https://www.proquest.com/docview/389048364/ | title=IBM Seeking New Success After PC: 1991 Shaping Up as a Pivotal Year for Computer Firm | journal=Sun Sentinel | page=1D | via=ProQuest}} By 1991, it was the best selling x86-based PC globally. 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. The heretofore best-selling PS/2 Model 50 Z, meanwhile, sold only 18,000 in a single month (October 1988).{{cite journal | last=LaPlante | first=Alice | date=December 12, 1988 | url=https://books.google.com/books?id=CjoEAAAAMBAJ&pg=PT4 | title=Survey Shows MCA Products Catching On | journal=InfoWorld | publisher=IDG Publications | volume=10 | issue=50 | page=5 | via=Google Books}} This represented a reversal of fortunes for the PS/2 line, which had underperformed as a whole compared to IBM's earlier PC line.{{cite journal | last=Kalpan | first=Alan | date=September 1991 | url=https://link.gale.com/apps/doc/A11134453/GPS?sid=wikipedia | title=IBM's counter-clones | journal=PC World | publisher=IDG Publications | volume=9 | issue=9 | pages=105 et seq | via=Gale}} The Model 55 SX proved so popular that IBM reported parts shortages in April 1990.{{cite journal | last=LaPlante | first=Alice | date=April 30, 1990 | url=https://books.google.com/books?id=LjsEAAAAMBAJ&pg=PP1 | title=PS/2 Model 50Z, 55 SX in Short Supply | journal=InfoWorld | publisher=IDG Publications | volume=12 | issue=18 | pages=1, 101 | via=Google Books}}

Apple Computer eventually overtook IBM for the number one spot in U.S. computer sales with the Macintosh Classic in June 1991.{{cite journal | last=Hooper | first=Laurence | date=June 6, 1991 | url=https://www.proquest.com/docview/398276472/ | title=IBM to Unveil 3 New Models for Its PC Line | journal=The Wall Street Journal | publisher=Dow Jones & Company | page=B4 | via=ProQuest}} However, it retained its status as the best-selling PC-compatible for the remainder of 1991 and the first half of 1992.{{cite journal | last=Hildebrand | first=Carol | date=January 27, 1992 | url=https://books.google.com/books?id=2yy5OVr3CzUC&pg=PA4 | title=IBM to pump up midrange PC line | journal=Computerworld | publisher=IDG Publications | volume=XXVI | issue=4 | page=4 | via=Google Books}}{{cite journal | last=Staff writer | date=May 1992 | url=https://archive.org/details/pcworld105unse/page/86/ | title=Best-Sellers | journal=PC World | publisher=IDG Publications | volume=10 | issue=5 | page=84 | via=the Internet Archive}} IBM officially withdrew the PS/2 Model 55 SX in May 1992, replacing it with the similarly specced PS/2 Models 56 and 57.{{cite journal | last=Staff writers | date=February 26, 1992 | url=https://www.proquest.com/docview/388915295/ | title=Chips That Zip | journal=Sun Sentinel | page=3D | via=ProQuest}}

Despite its massive sales success, the Model 55 SX received mixed, generally negative, reviews in the press. Despite earning an Editors' Choice Award in PC Magazine in 1990,{{cite journal | last=Ray | first=Garry | date=July 1990 | url=https://link.gale.com/apps/doc/A8617104/GPS?sid=wikipedia | title=The 386SX blizzard: how to distinguish among the more than 100 machines available | journal=Lotus | publisher=Lotus Publishing | volume=6 | issue=7 | pages=84 et seq | via=Gale}} 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 drive for being slow.{{rp|136}} InfoWorld{{'s}} Eugene Wong called the Model 55 SX slower than most other 16-MHz 386SX machines despite being significantly more expensive.{{cite journal | last=Wong | first=Eugene | date=September 4, 1989 | url=https://books.google.com/books?id=xDAEAAAAMBAJ&pg=PT95 | title=IBM's 55 SX Is Slower Than Most Other 16-MHz PCs | journal=InfoWorld | publisher=IDG Publications | volume=11 | issue=36 | pages=84–85 | via=Google Books}} 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.{{cite journal | last=Lockwood | first=Russ | date=August 1989 | url=https://www.proquest.com/docview/199381781/ | title=80386SX Performance Trials | journal=Personal Computing | publisher=VNU Business Information Services | volume=13 | issue=8 | pages=87–98 | via=ProQuest}} 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.{{cite journal | last=Byers | first=T. J. | date=December 1989 | url=https://link.gale.com/apps/doc/A7895494/GPS?sid=wikipedia | title=IBM PS/2 Model 55 SX | journal=PC World | publisher=IDG Publications | volume=7 | issue=12 | pages=124 et seq | via=Gale}}

{{See also|List of IBM PS/2 models}}

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{{IBM personal computers}}

55 SX

Category:Computer-related introductions in 1989