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IBM PS/2 Model 50 Z

From Alfawiki
IBM Personal System/2 Model 50
Company typeProduct line
IndustryComputer hardware
FoundedApril 2, 1987; 39 years ago (1987-04-02)
Headquarters
Boca Raton
,
United States
ProductsPersonal computer (IBM PS/2 Model 50 and Model 50 Z)

The Personal System/2 Model 50 represents a mid-tier desktop computer within IBM's Personal System/2 (PS/2) lineup. Launched in April 1987, it is powered by a 10 MHz Intel 80286 CPU. In June 1988, IBM refreshed this series with the Model 50 Z, which featured faster RAM that eliminated wait states found in the original version, thereby enhancing overall system speed. The Model 50 became the leading PS/2 model in sales for several years, with initial year sales exceeding 440,000 units.

Development and release

Unveiled on April 2, 1987, alongside the entry-level Model 30 and the higher-end Model 60, the Model 50 and Model 60 introduced IBM's exclusive Micro Channel architecture (MCA) bus to the market, intended as a successor to the older Industry Standard Architecture (ISA). Positioned as a midrange solution, the Model 50 was priced at $3,595 compared to the $2,295 cost of the base Model 30 that utilized an ISA bus. The Model 50 featured a desktop-style case, while the Model 60 came in a tower form factor with increased drive bays and expansion slots.

Produced at IBM’s Boca Raton, Florida plant, daily output reached approximately 1,000 units by June 1987. The strong demand for the Model 50 resulted in component shortages by the end of that year. IBM sold over 440,000 units during its first twelve months on the market and anticipated selling an additional 650,000 in 1988. By April of that year, it had become the best-selling personal computer globally and maintained this status through late 1989.

Specifications

The Model 50 was the most cost-effective PS/2 model equipped with Micro Channel architecture (MCA) expansion capabilities, providing four MCA slots compared to eight in the Model 60. As with all MCA-based PS/2 systems, it lacked support for ISA expansion cards. It also stood as the least expensive PS/2 to incorporate a Video Graphics Array (VGA) interface, delivering superior color depth and resolution relative to the older Enhanced Graphics Adapter (EGA). The chassis volume was roughly half that of its predecessor, the PC/AT, and it housed an Intel 80286 processor clocked at 10 MHz. Storage included a single 3.5-inch floppy disk drive, replacing earlier models’ use of larger 5.25-inch drives.

A key design element was its mostly tool-free disassembly process: two thumbscrews located on the rear allowed quick removal of the cover. Internally, both hard disk and floppy drives were installed on a platform above the motherboard that could be detached using captive push-pin tabs along with IBM’s provided plastic wedge tool ("crowbar"). Expansion cards were secured with plastic thumbscrews for easy removal.

The initial Model 50 utilized relatively slow 125-nanosecond DRAM modules, which introduced wait states during memory access and led to reduced system responsiveness. On June 2, 1988, IBM launched the Model 50 Z variant featuring faster 85-nanosecond DRAM chips that delivered roughly a 20% increase in performance. Additionally, the original dual SIMM slots were replaced by a single slot compatible with larger capacity SIMMs of either 1 MB or 2 MB (up from the previous maximum of 512 KB). The Model 50 Z also provided optional upgrades to faster hard drives of either 30 MB or 60 MB capacity, both offering seek times twice as quick as the original 20 MB drive.

Reception and legacy

Upon its release, the Model 50 garnered a range of opinions. It was commended for its cost-effectiveness and innovative hardware features, yet faced criticism due to hardware glitches, subpar computational speed, and a slow-performing standard hard drive. Nevertheless, PC Magazine subsequently acknowledged it as one of the most impactful personal computers spanning from the 1980s through the 2020s. The publication highlighted its significant contribution to the widespread adoption of VGA graphics and 3.5-inch floppy disk drives, as well as its tool-free design that set a precedent for subsequent PC designs.

Submodels

IBM PS/2 Model 50 Variants
Model IBM P/N Processor Clock speed
(MHz)		 Bus Number of
slots		 Number of
drive bays		 FDD HDD Standard
RAM		 Maximum
RAM		 Video adapter Monitor Form factor Release date Notes Ref(s).
50 8550-021 Intel 80286 10 (1 w) MCA, 16-bit 4 3 one 1.44 MB 20 MB (ST-506) 1 MB 1 MB VGA optional Desktop Template:Date table sorting [1][2]
50 Z 8550-031 Intel 80286 10 (0 w) MCA, 16-bit 4 3 one 1.44 MB 30 MB (ST-506) 1 MB 2 MB VGA optional Desktop Template:Date table sorting [3][2]
50 Z 8550-061 Intel 80286 10 (0 w) MCA, 16-bit 4 3 one 1.44 MB 60 MB (ESDI) 1 MB 2 MB VGA optional Desktop Template:Date table sorting [3][2]
  1. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named GJAN-43VM6G
  2. ↑ 2.0 2.1 2.2 Cite error: Invalid <ref> tag; no text was provided for refs named bowldspp338339
  3. ↑ 3.0 3.1 Cite error: Invalid <ref> tag; no text was provided for refs named GJAN-43VMLQ
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