IBM Personal Computer XT 286
| Company type | Personal computer model |
|---|---|
| Industry | Computer hardware |
| Predecessor | IBM PC (model 5150) |
| Founded | March 8, 1983 |
| Founder | International Business Machines Corporation (IBM) |
| Defunct | 1987 |
| Fate | Discontinued, succeeded by IBM PS/2 Model 30 |
| Successor | IBM PS/2 Model 30 |
Area served | Worldwide |
| Products | Personal computer |
| Owner | IBM |
| Parent | IBM |
The IBM Personal Computer XT (model 5160, commonly referred to as the PC/XT) represents the second installment in IBM's Personal Computer series, introduced on March 8, 1983. It bears a strong resemblance to the initial IBM PC model 5150 released in 1981, but incorporates significant upgrades such as an integrated hard disk drive and an increased number of expansion slots.
Name
IBM never officially clarified the meaning of "XT" on the device or in its documentation; however, some interpretations suggest it stands for "eXtended Technology" or simply "eXTended."
Features
The XT was designed as a progressive enhancement over the original PC, featuring several notable advancements:
- Expansion slots expanded from five to eight
- Minimum base RAM raised to 128 KB
- ROM configuration changed from five 8KB chips to two 32KB chips
- Most units came equipped with a 10 MB hard drive and a disk controller utilizing Xebec integrated circuits
- Preloaded with PC DOS version 2.0
- The 5-pin DIN cassette interface connector was eliminated
Aside from these updates, other specifications largely matched those of the original IBM PC.
Expansion slots
With only five expansion slots, the original IBM PC quickly encountered limitations since essential peripherals—such as video adapters, disk controllers, and printer interfaces—each required dedicated cards, often occupying all available slots and compelling users to swap cards frequently. Some clone manufacturers resolved this by integrating multiple components onto the motherboard, thereby freeing up slots. Additionally, peripheral vendors developed multifunction cards that combined several functions into a single expansion card.
The XT addressed this constraint by increasing the number of expansion slots to eight. Although these slots are compatible with those in the original PC, two of the additional slots located behind the hard drive bay cannot accommodate full-length cards due to chassis space restrictions. Furthermore, the narrower spacing between slots restricts the installation of certain multi-board expansion cards.
Expansion unit
The 5161 Expansion Unit shares the same chassis and power supply design as the XT but replaces the mainboard with a backplane containing eight card slots. This unit connects to the primary system through an Extender Card and Receiver Card linked by a proprietary cable. The 5161 comes with a 10 MB hard disk and room for an additional drive; it also supports extra memory modules. However, memory installed within this expansion operates with wait states because of the extender card interface, making memory installed in the main unit preferable for performance.
Compatible with both the XT and the original IBM PC (model 5150), the 5161 provided users with enhanced storage capacity and further expansion possibilities beyond what was available in the base system.
Other features
PC DOS version 2.0 introduced a floppy disk format featuring nine sectors per track, which increased storage capacity to 180K for single-sided disks and 360K for double-sided disks, compared to earlier formats of 160K/320K.
During its initial two years on the market, the XT was not sold as a floppy-only configuration; users desiring a second floppy drive needed to acquire the separate 5161 expansion chassis. The XT incorporated IBM BASIC stored in ROM and displayed a memory size count during POST—a feature not present in the original PC.
The desktop case design closely resembles that of its predecessor, weighing approximately 32 pounds and measuring around 19.5 inches wide by 16 inches deep by 5.5 inches tall.
Similar to the original model, the XT motherboard included a socket for an optional Intel 8087 floating-point coprocessor, which accelerated computation-intensive applications like CAD software when supported.
The power supply was upgraded to deliver 130 watts compared to that of the original PC. While U.S. versions operated exclusively on 120 V AC power, later international releases supported 240 V mains input but retained the same wattage specification.
Revisions and Variants
IBM introduced multiple variations of the XT model.
One notable version, the 3270 PC, incorporated 3270 terminal emulation and was launched in October 1983.
The 068 and 078 submodels, released in 1985, featured dual-floppy disk configurations without hard drives, while also debuting the Enhanced Graphics Adapter and Professional Graphics Adapter as available display options.
By 1986, models equipped with motherboards supporting 256 to 640 KB of memory transitioned to using half-height disk drives.
Submodels 268, 278, and 089 were outfitted with 101-key keyboards—these were modified IBM Model M units operating under XT protocols but lacked LED indicators.
In contrast, submodels 267, 277, and 088 retained the original keyboard design but upgraded storage by adding 3.5" floppy drives and replacing full-height 10 MB hard disks with half-height 20 MB Seagate ST-225 drives.
The submodel 788 uniquely offered a standard Color Graphics Adapter among XT variants.
Submodels 568, 588, and 589 served as the foundation for the XT/370, which included an extra co-processor board enabling execution of System/370 instructions. Additionally, an XT model featuring a Series/1 co-processor existed under the IBM 4950 designation but was assigned a distinct system unit number.
XT 286
In 1986, IBM unveiled the XT 286 (model number 5162), powered by a 6 MHz Intel 80286 CPU. Positioned below the IBM AT in the product hierarchy, it sometimes outperformed comparable AT models with similar processors due to its zero-wait state memory design.
Standard specifications included 640 KB of RAM, a high-density AT-style 1.2 MB floppy drive, and a 20 MB hard disk. Despite these features, it faced criticism for offering limited value relative to its price.
The XT 286 was equipped with a flexible 157-watt power supply capable of operating on either 115 or 230 V AC input voltages.
Both the original XT and the XT/286 models were phased out by late 1987 following the introduction of the Personal System/2 series. Within this new lineup, the XT was effectively succeeded by the 8086-based IBM PS/2 Model 30, which preserved compatibility with the XT’s original 8-bit ISA bus instead of adopting the PS/2’s Micro Channel architecture used in higher-end configurations.
Comparison Table
| Template:Verth | Template:Verth | Date Announced | Date Discontinued | Bus | Template:Verth | Template:Verth | Processor | Template:Verth | Template:Verth | Template:Verth | FDD | HDD | Notes | Ref(s). |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Template:Verth | Template:Verth | Template:Date table sorting | Template:Date table sorting | ISA, 8-bit |
8 | 2 | Intel 8088 | 4.77 | 128 KB | 640 KB | 360 KB | 10 MB | ||
| Template:Verth | Template:Verth | Template:Date table sorting | Template:Date table sorting | ISA, 8-bit |
8 | 2 | Intel 8088 | 4.77 | 256 KB | 640 KB | 360 KB | 10 MB |
Reception
The XT garnered positive feedback, with the release of PC DOS 2.0 regarded as a more impactful advancement than the hardware enhancements. By the end of 1983, IBM was able to sell all units manufactured. Nonetheless, by 1985, the IBM PC AT had mostly replaced the XT for the majority of users.
See also
References
- Notes
- IBM (1983). Personal Computer Hardware Reference Library: Guide to Operations, Personal Computer XT. IBM Part Number 6936831.
External links
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