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IBM Personal Computer XT
IBM Personal Computer XT
IBM Personal Computer XT
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IBM Personal Computer XT
Also known asIBM XT, PC/XT, XT
ManufacturerIBM
TypePersonal computer
Release dateMarch 8, 1983; 42 years ago (1983-03-08)
DiscontinuedApril 1987 (1987-04)
Operating systemIBM BASIC / PC DOS 2.0-3.20 / PC/IX / SCO Xenix
CPUIntel 8088 @ 4.77 MHz
Memory128 KB – 640 KB
Storage10–20 MB hard drive
GraphicsMDA, CGA
SoundPC speaker 1-channel square-wave/1-bit digital (PWM-capable)
Power120/240 VAC
DimensionsW: 19.5 in (50 cm)
H: 5.5 in (14 cm)
D: 16 in (41 cm)
Weight32 lb (15 kg)
PredecessorIBM Personal Computer
Successor
RelatedList of IBM Personal Computer models

The IBM Personal Computer XT (model 5160, often shortened to PC/XT) is the second computer in the IBM Personal Computer line, released on March 8, 1983.[1] Except for the addition of a built-in hard drive and extra expansion slots, it is very similar to the original IBM PC model 5150 from 1981.

Name

[edit]

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

[edit]

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
  • 5x8 KB ROM ICs was replaced by 2x32 KB one
  • A 10 MB hard drive was included on most sub-models, with a disk controller featuring Xebec ICs[4]: 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

[edit]

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.[7][8]

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.[3][8]

Expansion unit

[edit]

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.[3] The 5161 shipped with a 10 MB hard drive, and had room for a second one.[8]

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).[9]

Other features

[edit]

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.[3]

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.[8]

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.[10]

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.[10] XTs with 240 V-compatible power supplies were later sold in international markets. Both were rated at 130 watts.[11]

Revisions and variants

[edit]
IBM PC/XT 5160 dual floppy drives with 5153 Color Monitor

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.[10]

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.[11]

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.[11] 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.[12]

XT 286

[edit]
XT 286 badge
XT 286 badge

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.[10]: 95 

It shipped with 640 KB RAM standard, an AT-style 1.2 MB high-density diskette drive and a 20 MB hard disk.[13][14] Despite these features, reviews rated it as a poor market value.[15]

The XT 286 uses a 157-watt power supply, which can internally switch between 115 or 230 V AC operation.[13]

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

[edit]
See also: List of IBM Personal Computer models
IBM Personal Computer XT models
Type
IBM P/N
 Date announced Date withdrawn Bus
No. of slots
No. of bays
 Processor
Clock speed
(MHz)
Stock onboard RAM
(KB)
Maximum onboard RAM
(KB)
 FDD HDD Notes Ref(s).
XT
5160-087
 March 1983 June 1984 ISA,
8-bit 		8 2 Intel 8088 4.77 128 KB 640 KB 360 KB 10 MB  
XT
5160-086
 June 1984 June 1987 ISA,
8-bit 		8 2 Intel 8088 4.77 256 KB 640 KB 360 KB 10 MB  
XT
5160-068
 April 1985 June 1987 ISA,
8-bit 		8 2 Intel 8088 4.77 256 KB 640 KB 360 KB none  
XT
5160-078
 April 1985 June 1987 ISA,
8-bit 		8 2 Intel 8088 4.77 256 KB 640 KB two 360 KB none  
XT
5160-088
 April 1986 June 1987 ISA,
8-bit 		8 2 Intel 8088 4.77 512 KB 640 KB 360 KB 20 MB Shipped with original IBM PC "Model F" keyboard
XT
5160-089
 April 1986 June 1987 ISA,
8-bit 		8 2 Intel 8088 4.77 512 KB 640 KB 360 KB 20 MB Shipped with Enhanced Keyboard
XT
5160-267
 April 1986 June 1987 ISA,
8-bit 		8 2 Intel 8088 4.77 256 KB 640 KB 360 KB none Shipped with original IBM PC "Model F" keyboard
XT
5160-268
 April 1986 June 1987 ISA,
8-bit 		8 2 Intel 8088 4.77 256 KB 640 KB 360 KB none Shipped with Enhanced Keyboard
XT
5160-277
 April 1986 June 1987 ISA,
8-bit 		8 2 Intel 8088 4.77 256 KB 640 KB two 360 KB none Shipped with original IBM PC "Model F" keyboard
XT
5160-278
 April 1986 June 1987 ISA,
8-bit 		8 2 Intel 8088 4.77 256 KB 640 KB two 360 KB none Shipped with Enhanced Keyboard
5271-000
 Unknown July 1987 ISA,
8-bit 		8 2 Intel 8088 4.77 256 KB 640 KB 360 KB none Without printer adapter, fixed disk adapter, and keyboard
5271-002
 October 1983 July 1987 ISA,
8-bit 		8 2 Intel 8088 4.77 256 KB 640 KB 360 KB none Without printer adapter and fixed disk adapter
5271-004
 October 1983 July 1987 ISA,
8-bit 		8 2 Intel 8088 4.77 320 KB 640 KB 360 KB none Without fixed disk adapter; stock onboard RAM increased to 384 KB in June 1984
5271-006
 October 1983 July 1987 ISA,
8-bit 		8 2 Intel 8088 4.77 320 KB 640 KB 360 KB 10 MB With fixed disk adapter; stock onboard RAM increased to 384 KB in June 1984
5160-568
 October 1984 April 1987 ISA,
8-bit 		8 2 Intel 8088 4.77 256 KB 640 KB 360 KB none
5160-588
 October 1984 April 1987 ISA,
8-bit 		8 2 Intel 8088 4.77 256 KB 640 KB 360 KB 10 MB
5160-589
 October 1984 April 1987 ISA,
8-bit 		8 2 Intel 8088 4.77 256 KB 640 KB 360 KB 10 MB
XT Model 286
5162-286
 September 1986 October 1987 ISA,
16-bit 		8 2 Intel 80286 6 640 KB 640 KB 1.2 MB 20 MB  

Reception

[edit]

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.[29] By 1985 the IBM PC AT made the XT obsolete for most customers.[30]

Timeline

[edit]
Timeline of the IBM Personal Computer
IBM ThinkCentreIBM NetVistaIBM Palm Top PC 110IBM PC SeriesIBM AptivaIBM PS/ValuePointThinkPadEduQuestIBM PS/noteAmbra Computer CorporationIBM PCradioIBM PS/1IBM PS/55IBM PS/2IBM Personal Computer XT 286IBM PC ConvertibleIBM JXIBM Personal Computer AT/370IBM Personal Computer ATIBM Industrial ComputerIBM PCjrIBM Portable Personal ComputerIBM Personal Computer XT/370IBM 3270 PCIBM Personal Computer XTIBM 5550IBM Personal ComputerIBM System/23 DatamasterIBM 5120IBM 5110IBM 5100
Asterisk (*) denotes a model released in Japan only

See also

[edit]

References

[edit]
[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

IBM Personal Computer XT

View on Grokipedia
from Grokipedia
The IBM Personal Computer XT (model 5160), released on March 8, 1983, was the second model in IBM's Personal Computer line and the first to include a built-in hard disk drive as standard equipment, significantly advancing storage capabilities for business and professional users. Priced at $4,995 for the base configuration, it featured an Intel 8088 microprocessor running at 4.77 MHz, 128 KB of RAM expandable to 640 KB, a 10 MB fixed disk drive, and a 360 KB 5.25-inch floppy disk drive. Developed as an extension of the original PC (model 5150) introduced in 1981, the XT—standing for "eXtended Technology"—retained the same and expansion capabilities while adding enhanced memory and storage to support more demanding applications like database management and word processing. It included eight expansion slots for peripherals, compatibility with IBM PC-DOS 2.0, and optional adapters for monochrome or color displays, making it a versatile platform for the emerging personal computing market. The system's design emphasized productivity, with features like a 40 KB ROM containing and self-test diagnostics, allowing users to expand storage up to 20 MB via an optional unit. The XT played a pivotal role in establishing the IBM PC as the industry standard for business , encouraging third-party hardware and due to its and widespread adoption in offices. By integrating fixed storage, it reduced reliance on floppy disks and accelerated the shift toward hard drive-equipped personal computers, influencing subsequent models like the IBM PC AT. Production continued until 1987, with revisions including upgraded power supplies and enhanced graphics options, solidifying its legacy in history.

Overview

Model Designation and Naming

The IBM XT carries the official model number 5160 and stands as the second computer in IBM's Personal Computer line. It functions as the direct successor to the original model 5150, building upon its foundational architecture. The "XT" designation signifies "eXtended Technology," a term chosen to highlight the model's expanded features, such as additional expansion slots that broadened peripheral compatibility beyond the capabilities of the initial PC. This naming convention underscored IBM's intent to evolve the platform incrementally while maintaining compatibility with existing software and hardware. In common usage, the system is frequently abbreviated as PC/XT or simply XT, reflecting its role as an accessible upgrade in the personal computing market. Notably, the XT marked the first IBM Personal Computer to incorporate integrated fixed storage as a standard element, setting it apart from earlier models that relied on optional external drives.

Release and Initial Pricing

The IBM Personal Computer XT, model 5160, was unveiled on March 8, 1983, as the successor to the original IBM PC, offering an upgrade path for existing users through its integrated hard disk drive and expanded capabilities. The "XT" designation stood for eXtended Technology, reflecting enhancements like additional memory and storage options. This release marked IBM's push to solidify its position in the burgeoning personal computer market by addressing demands for more robust business applications. The base model was priced at $4,995, which included 128 KB of RAM, a 10 MB , a single 360 KB 5.25-inch drive, a monochrome display adapter, and a keyboard. Adjusted for , this equates to approximately $16,250 in 2025 dollars. Customers could opt for upgrades at purchase, such as additional RAM up to 640 KB or a second floppy drive, with the fully configured system reaching around $6,000. The XT was distributed exclusively through IBM's network of authorized dealers, ensuring professional sales support and service. Each unit shipped with PC DOS 2.0 as the bundled operating system, which introduced hard disk support and features like subdirectories and file copying commands, enabling efficient formatting and management of the integrated drive. This version of DOS was essential for leveraging the XT's storage advancements, distinguishing it from the floppy-only original PC.

Development

Background and Origins

The IBM Personal Computer (model 5150), released on August 12, 1981, marked IBM's entry into the personal computing market, but its reliance on drives for storage limited its appeal in business environments where users required greater capacity for data-intensive applications. This floppy-only configuration, while innovative for its time, drew feedback from early adopters highlighting the need for more robust storage solutions to support expanding enterprise workflows. Strategically, IBM sought to solidify its position in the burgeoning enterprise sector by evolving the original PC into a more capable system, integrating fixed-disk storage to address these limitations and better serve professional users. Under the leadership of Don Estridge, who headed the Entry Level Systems unit in , IBM shifted focus from its traditional mainframe dominance toward accessible personal systems that could integrate with larger corporate infrastructures. The unit, established to accelerate PC innovation outside IBM's conventional bureaucracy, aimed to leverage the original PC's —which had unexpectedly generated $1 billion in sales during its first year—to capture a larger share of the business market. Market pressures intensified this evolution, as competitors like began cloning IBM-compatible systems, with the launching in November and rapidly eroding IBM's lead by offering similar functionality at competitive prices. Estridge's team responded by initiating development of the XT (model 5160) in , building directly on the 5150's success to enhance expandability and storage while maintaining compatibility. This timeline reflected IBM's urgency to sustain momentum in a market growing at an unprecedented rate, with personal computing transitioning from novelty to essential business tool.

Design Process

The design of the IBM Personal Computer XT (model 5160) was led by engineers at IBM's Entry Level Systems unit in Boca Raton, Florida, who built upon the architecture of the original IBM PC (model 5150) to address limitations in storage and expandability while prioritizing seamless integration. The team modified the existing 5150 motherboard, a multilayer board measuring 8.5 by 12 inches, to incorporate a dedicated fixed disk controller and BIOS support for hard disk operations, including revectoring of the diskette parameter table at vector 40h and fixed disk parameters at vector 41h, with primary disk I/O services handled via INT 13h. This approach allowed for rapid development by reusing proven components like the Intel 8088 processor and 8-bit external bus, ensuring the XT remained software-compatible with the 5150 and its peripherals. A primary was the addition of three extra expansion slots, increasing the total from five to eight 62-pin ISA slots, which supported up to 1 MB of addressing via a 20-bit bus and enhanced modularity for optional adapters such as expansions and communications modules. To provide built-in , the design integrated a 10 MB Seagate ST-412 as standard, featuring 306 cylinders, 4 heads, 17 sectors per track, and MFM encoding, with thermal isolation to enable immediate read/write access after power-up. The system emphasized 100% with 5150 software and hardware, achieved through consistent BIOS interrupts (hex 10-1A), I/O channel designs, and ROM scanning in 2K blocks from C8000 to F4000. Engineering challenges included powering the new hard drive, which required upgrading the power supply from 63 W in the 5150 to 130 W, delivering outputs such as +5 Vdc at 15 A and +12 Vdc at 4.2 A, along with over-voltage protection to handle the increased load. The standard configuration included the Monochrome Display Adapter (MDA) with a CRT controller for high-resolution text output, also incorporating an onboard parallel printer port to support business-oriented applications without compromising the original PC's display compatibility. These decisions focused on enhancing reliability and usability, such as improved error correction with 11-bit burst detection and ECC for disk operations, while maintaining the open-architecture philosophy.

Specifications

Processor and Memory

The IBM Personal Computer XT (model 5160) featured an microprocessor as its , operating at a clock speed of 4.77 MHz. This processor employed a 16-bit internal architecture for computations while utilizing an 8-bit external data bus for communication with and peripherals, which limited data transfer bandwidth but balanced cost and performance for business applications of the era. The 8088 also incorporated a 20-bit address bus, enabling access to up to 1 MB of total addressable memory space. Memory in the XT consisted of a base configuration of 128 KB of (DRAM) installed on the system board, utilizing 16 Kbit DRAM chips arranged in four banks with parity checking for error detection. This RAM was expandable up to 640 KB of through additional on-board modules or expansion slots, with support for chip densities including 16 K × 1, 32 K × 1, and 64 K × 1 bit modules having access times of 250 ns or faster. The (ROM) remained unchanged from the original PC (model 5150), totaling 40 KB to store the and a , ensuring compatibility with existing software. The system's bus architecture was the 8-bit (ISA), running at 4.77 MHz to match the processor clock, which facilitated direct connections for and I/O devices while supporting the 640 KB limit for DOS-accessible RAM. This bus design used a 62-pin per slot, provided three DMA channels and six levels, and operated with standard TTL voltage levels including +5 V and ±12 V. An optional numeric coprocessor could be installed in a dedicated socket on the adjacent to the 8088, accelerating operations through an 80-bit wide internal data path and eight 80-bit registers for tasks like scientific computations.

Storage and I/O Interfaces

The IBM Personal Computer XT introduced a significant advancement in storage by including a built-in hard disk drive as standard equipment, marking the first time an IBM PC model shipped with this feature. The drive was a Seagate ST-412, providing 10 MB of capacity using Winchester technology, which sealed the read/write heads and disks within the unit to minimize contamination and improve reliability. This configuration represented a substantial upgrade over the original IBM PC's reliance solely on floppy disks, enabling faster data access and larger storage for business applications. Later production models and user upgrades supported expansion to 20 MB capacity, often by replacing the ST-412 with drives like the Seagate ST-225 while maintaining compatibility with the system's architecture. For removable storage, the XT came standard with one 5.25-inch floppy disk drive, offering 360 KB capacity in double-sided, double-density format. This drive used the same 40-track, 9-sector-per-track configuration as the original PC but benefited from the XT's enhanced and space, allowing for full-height installation without external enclosures. The floppy controller, integrated into the , supported up to four drives total via daisy-chaining, though the standard setup used the drive for both the operating system and data exchange. The XT's input/output interfaces were designed for compatibility with existing peripherals while providing essential connectivity for office environments. It featured a single RS-232 serial port for connecting modems, terminals, or serial printers, using a 9-pin male D-sub connector compliant with EIA standards. An optional parallel port, compatible with Centronics interfaces, supported printers and other parallel devices via a 25-pin female D-sub connector, enabling bidirectional data transfer at up to 50 KB/s in practice. Additionally, a cassette port was included for low-cost data storage using audio tapes, though it saw minimal use due to the prevalence of floppy drives; this port used a 3.5 mm mono jack for input/output. The keyboard connected via a 5-pin circular DIN connector, supporting the XT-specific 83-key layout with scan codes for enhanced input reliability, while mouse support was typically added through the serial port or optional adapters. The hard disk drive's operation was managed by the 1210 controller card, which occupied one of the system's eight expansion slots and implemented (MFM) encoding for data transfer rates up to 5 Mbit/s. This controller handled the ST-506/ST-412 interface protocol, including seek operations and error correction, and was optimized for the XT's single-geometry support of 306 cylinders, 4 heads, and 17 sectors per track. The power supply, rated at 130 watts, adequately supported the drive's startup demands, ensuring stable performance without additional modifications.

Graphics and Sound

The IBM Personal Computer XT (Model 5160) featured graphics capabilities inherited from the original PC, primarily through optional adapters such as the Monochrome Display Adapter (MDA) for text-based output. The MDA supported a text-only mode of 80 columns by 25 rows, utilizing a 9x14 character box with attributes such as underline, reverse video, normal intensity, and high intensity, all rendered in on a direct-drive monitor operating at 18 kHz horizontal frequency. This setup provided clear, high-contrast display for business applications but lacked any graphical rendering, limiting visual output to character-based interfaces. For color and basic graphics, the XT offered the optional (CGA), which expanded on the MDA's text capabilities while introducing limited graphical modes. The CGA supported 80x25 in color (with 16 foreground and 8 background colors, plus blinking) or , alongside 40x25 , all using an 8x8 character box. In graphics modes, it provided 320x200 resolution with 4 colors or 640x200 (or 2 colors), enabling simple pixel-addressable output for early games and applications, though color fidelity was constrained by the palette and monitor type. Display compatibility centered on 80-column text modes across both adapters, selectable via DIP switches and settings, ensuring broad support for standard CRT monitors connected through dedicated I/O ports. Advanced graphics, such as those offered by the third-party Hercules Graphics Card (HGC) for 720x348 monochrome resolution in addition to 80x25 text, were not standard on the XT and required installation in an expansion slot. The system's graphics thus emphasized reliability for text-heavy professional use over visual sophistication, with no native support for higher resolutions or enhanced color depth; users reliant on more demanding graphical tasks had to depend on aftermarket expansion cards for improvements. The XT's sound capabilities were equally basic, relying on an integrated without any dedicated or multichannel audio hardware. This 2-1/4 inch permanent-magnet speaker, rated at approximately 1/2 watt, produced monophonic output driven by the system's (specifically channel 2) to generate square-wave tones or simple 1-bit digital signals via . Common uses included short (1-second) or long (3-second) beeps at around 1000 Hz for system feedback, error diagnostics (e.g., one long and two short beeps for video issues), and basic alerts in software, all controlled programmatically through port I/O. Lacking provisions for complex waveforms, sampled audio, or , the speaker served primarily as an auditory cue for user interaction rather than entertainment or , underscoring the XT's focus on utilitarian .

Expansion and Accessories

Built-in Expansion Slots

The IBM Personal Computer XT featured eight built-in expansion slots on its system board, a significant increase from the five slots in the original IBM PC model 5150, providing greater flexibility for peripheral integration in business environments. These slots adhered to the 8-bit (ISA) bus, utilizing 62-pin card edge-sockets to connect adapters directly to the system's I/O bus. Of the eight slots, five were full-length to accommodate standard cards, while three were half-height, limited by the placement of the internal and floppy drive bays, though all supported the same electrical interface. In a typical configuration, one slot was occupied by the fixed disk adapter for the built-in 10 MB hard drive, leaving the remaining seven available for user expansions such as additional memory cards or I/O adapters; the motherboard itself included sockets for an optional 8087 math coprocessor, which did not require a dedicated slot. Power for the slots was supplied by the system's 130-watt power supply unit, delivering key voltage rails including +5 Vdc at up to 15 A, -5 Vdc at 300 mA, +12 Vdc at 4.2 A, and -12 Vdc at 250 mA, enabling reliable operation of connected devices. Each slot could support up to 64 KB of memory expansion, contributing to the overall system limit of 640 KB when combined with onboard RAM. This expansion architecture was particularly suited for business applications, allowing the installation of networking cards like the Asynchronous Communications Adapter for serial connections and modems, as well as configurations for multi-user setups through additional I/O channels. The design emphasized modularity, enabling users to tailor the XT for tasks such as in office networks or enhanced communications without relying on external chassis.

External Expansion Unit

The IBM Expansion Unit, model 5161, was an optional external chassis released in early 1983 alongside the Personal Computer XT to extend its expandability for business environments. This unit connected to the XT system unit through a 56-wire, foil-shielded equipped with 62-pin D-shell male connectors, requiring the installation of an extender card that occupied one internal ISA slot. The connection enabled seamless compatibility with the XT's 8-bit ISA bus, allowing the external slots to function as an extension of the internal ones. The 5161 housed eight ISA expansion slots, with seven usable after accounting for the receiver card, enabling a combined total of 14 slots when paired with the XT's remaining seven internal slots. It included a dedicated 130-watt switching providing +5V at 15A maximum, -5V at 0.3A maximum, +12V at 4.2A maximum, and -12V at 0.25A maximum, designed to independently power demanding peripherals without straining the XT's internal supply. This made it suitable for applications in small offices needing extensive I/O expansion, such as adding multiple hard disk drives or tape backup systems. Configurations of the 5161 typically included one 10 MB fixed disk drive, with provisions for a second drive in its internal bays, supporting up to 20 MB of total storage when integrated with the XT. Priced at approximately $2,600, the unit targeted users whose workloads exceeded the XT's built-in capacity, facilitating growth in storage and connectivity without replacing the core system.

Compatible Peripherals

The IBM Personal Computer XT utilized the same peripheral interfaces as the original IBM PC, enabling compatibility with a variety of IBM-designed and third-party devices to enhance input, output, storage, and connectivity options. IBM's standard peripherals included the 5151 Monochrome Display, a 12-inch CRT monitor with green phosphor that supported 80x25 text resolution when paired with the Monochrome Display Adapter for business applications requiring sharp character rendering. The 5153 Color Display, a 13-inch CRT offering 16 colors at 320x200 resolution or 640x200 monochrome, worked with the Color/Graphics Adapter to enable basic graphics and gaming. The standard input device was the 83-key IBM PC/XT keyboard (Model F, part number 1501100), featuring a buckling-spring mechanism and connected via a 5-pin DIN port for reliable typing in office environments. Optional output devices encompassed the 5152 Graphics Printer, a 9-pin dot-matrix model capable of 80 characters per second in draft mode and supporting both text and bit-image graphics via the parallel port. Third-party peripherals expanded the XT's networking and communication capabilities, often installed in its 8 expansion slots. The Hayes Smartmodem 300 (and later 1200 models) provided asynchronous at up to 1200 , compatible with the XT's or internal ISA cards for bulletin board access and remote data transfer. IBM's own PC Network baseband adapter enabled local area networking for up to 80 nodes at 2 Mbit/s, using twisted-pair cabling in daisy-chain style for office . SCSI controllers, such as early models like the AHA-100, allowed connection of larger hard drives (beyond the XT's built-in 10 MB) via the ISA bus, supporting -1 protocol for improved storage scalability in professional setups. Accessories for the 5161 Expansion Unit, an external providing additional slots and power, included extra 360 KB 5.25-inch floppy drives for backup and data interchange, as well as 3270 cards (e.g., IRMA or PC adapter) for mainframe connectivity in enterprise environments. Upgrade paths focused on memory and audio enhancements; RAM expansion cards, such as IBM's 128 KB or 256 KB options using 64Kx1 DRAM modules, allowed total system memory to reach 640 KB by filling addresses from 384 KB to 640 KB, essential for multitasking under . Post-release, the AdLib Music Synthesizer Card (1987), an 8-bit ISA add-on with a Yamaha YM3812 FM chip, provided 9 channels of sound for games and applications, fully compatible with the XT's architecture despite its original lack of built-in audio.

Variants

Original Model 5160

The Personal Computer XT, model 5160, was introduced on March 8, 1983, as an enhanced version of the original PC, featuring a built-in and additional expansion capabilities to support growing business needs. The base configuration included an processor running at 4.77 MHz, 128 KB of RAM (expandable to 256 KB shortly after launch and up to 640 KB total), a 10 MB Seagate ST-412 , and one 360 KB 5.25-inch double-sided floppy drive, with an option for a second floppy drive. Upgrade options allowed for a 20 MB hard drive and further memory expansions, making it adaptable for office applications requiring persistent storage. Production of the model 5160 ran from its 1983 debut until April 2, 1987, when it was discontinued alongside the original PC line in favor of the new (PS/2) series. During this period, IBM manufactured nearly 2.2 million units, reflecting strong demand in professional environments. As the first mass-market from a major manufacturer to include a built-in as standard, the XT significantly influenced adoption by enabling efficient handling of larger datasets and software installations without relying on external or floppy-based storage. This feature, combined with eight ISA expansion slots (six full-length and two half-length), positioned the XT as a reliable platform for productivity tools in corporate settings.

XT 286 Model 5162

The IBM Personal Computer XT 286, model 5162, represented a 1986 revision of the original XT line, introducing an processor clocked at 6 MHz with zero wait states to deliver enhanced performance over the 8088-based predecessor. Announced on September 2, , and available immediately thereafter, this model served as a transitional , offering 80286 capabilities in the familiar XT form factor while aiming to bridge the gap to the more advanced IBM PC AT series. The base configuration featured 640 KB of RAM on the board, which could be expanded up to 16 MB through the use of Expanded Memory Specification (EMS) adapter cards installed in the expansion slots. Standard storage included a 20 MB fixed hard disk drive and a 1.2 MB 5.25-inch high-capacity diskette drive, with options for additional drives such as a 360 KB 5.25-inch or 720 KB 3.5-inch unit. A Video Graphics Array (VGA) graphics option was available via compatible expansion cards, enabling higher-resolution display capabilities beyond the original XT's limitations. Priced at $3,995 for the base model, the XT 286 maintained broad backward compatibility with existing IBM PC family hardware and software, including peripherals from the Model 5160, while supporting PC-DOS 3.2 or later. Despite these upgrades, the XT 286 retained the XT's 8-bit ISA-compatible bus architecture alongside five 16-bit slots, resulting in performance bottlenecks for data-intensive 16-bit peripherals and I/O operations compared to full 16-bit AT systems. This design also meant it was not entirely compatible with all 80286-optimized software developed for the AT platform, often requiring bus adapters or modifications for seamless operation. Production of the model 5162 ended in spring 1987, coinciding with the discontinuation of the original XT as IBM shifted focus toward the Personal System/2 lineup.

Other Specialized Models

The IBM 3270 PC (model 5271), announced on October 18, 1983, was a specialized variant of the PC XT tailored for enterprise users needing seamless integration with systems. It incorporated dedicated hardware, including a 3270 display adapter and converged keyboard, to emulate the functionality of an terminal, enabling direct connectivity to host systems via for running mainframe applications like and . Standard features included 256 KB of RAM (expandable to 640 KB), two 360 KB floppy drives, and eight expansion slots, with four to seven occupied by the integrated 3270 components, preserving partial compatibility with standard PC peripherals. This model addressed the growing demand for hybrid workstations in corporate environments dominated by IBM's System/370 mainframes. The IBM PC XT/370, also announced in October 1983, extended the XT platform with mainframe emulation capabilities through a System/370 co-processor, allowing local execution of compatible software without relying on remote hosts. It consisted of three additional expansion cards installed in a standard XT chassis: a System/370 processor card using a for emulation, a 512 KB dynamic RAM card, and an I/O interface card supporting up to 1 MB of virtual storage under the VM/PC operating system. Targeted at developers and users transitioning mainframe workloads to desktops, the XT/370 supported single-user environments for testing and running legacy applications, but its complexity and high cost limited production to a small scale, primarily as an experimental bridge between personal and large-scale computing. In February 1984, IBM released the Portable Personal Computer (model 5155), a transportable adaptation of the XT designed for professionals requiring mobility without sacrificing desktop performance. Weighing about 30 pounds (13.6 kg) and encased in a suitcase-like form factor with a carrying handle, it featured an integrated 9-inch amber monochrome composite video display, 256 KB RAM (expandable to 640 KB), and compatibility with XT expansion cards via an internal bus. An optional 10 MB hard disk drive provided enhanced storage over floppy-only configurations, though the system relied on AC power rather than batteries, positioning it as a luggable rather than truly portable device. This model catered to field engineers and executives needing on-site computing power akin to the fixed XT. These niche variants, including the 3270 PC and XT/370, were discontinued in 1987, while the Portable PC was discontinued in April 1986, as IBM redirected resources toward the more advanced Personal System/2 family to consolidate its personal computing offerings.

Reception and Legacy

Critical and Market Reception

The IBM Personal Computer XT received positive critical reception upon its March 1983 release, particularly for its innovative integration of a hard disk drive and enhanced expandability, which addressed key limitations of the original IBM PC. In a detailed review published in the November 1983 issue of Byte magazine, author Rowland Archer Jr. praised the 10 MB hard drive for its seamless reliability, fast 5 Mbps transfer rate (compared to 250 Kbps for floppies), and substantial storage capacity, describing it as a major advancement that improved overall system performance for demanding tasks. The review also highlighted the XT's eight expansion slots—up from five in the original PC—and support for up to 640 KB of RAM, noting these features provided exceptional flexibility for adding peripherals and ensuring compatibility with existing IBM boards, making it a versatile platform for professional use. PC Magazine's October 1983 coverage commended the XT's robust engineering and built-in hard drive for delivering dependable performance in business environments, where reliable data handling was paramount. The system's design was seen as an essential upgrade for office settings, overcoming the storage and speed constraints of floppy-only systems to enhance productivity in tasks like document management and database operations. Despite these strengths, the XT faced criticisms for its high cost and limited standard graphics capabilities. The base configuration, priced at $4,995 including 128 KB RAM, the 10 MB hard drive, and a floppy drive, was viewed as expensive, especially when additional expenses for a monitor and DOS (over $600 more) were factored in, potentially limiting accessibility for smaller businesses. Graphics were another weak point, with the standard monochrome display and optional Color Graphics Adapter (CGA) supporting only 640 x 200 resolution in four colors criticized as inadequate compared to rivals like the Texas Instruments Professional PC, and prone to issues such as blinking in certain software. Media coverage positioned the XT as a professional-oriented of the PC line, with the November 1983 issue of Byte themed around "Inside the PC," framing the XT as the go-to machine for business professionals seeking reliability and scalability. By 1984, however, the introduction of the faster PC AT rendered the XT increasingly obsolete for users requiring advanced processing power, though it remained a staple in many offices for its proven durability.

Sales and Commercial Performance

The IBM Personal Computer XT contributed significantly to IBM's robust sales in the personal computer market following its March 1983 launch. In 1983, IBM's overall PC shipments reached approximately 750,000 units, exceeding initial forecasts and driven in part by the XT's introduction as an upgraded model with built-in storage. Over the XT's production lifespan from 1983 to 1987, IBM sold roughly 2.1 million units of the model, underscoring its commercial viability amid growing competition. The XT line helped propel IBM's PC division revenue, which generated $1 billion in the original PC's debut year of 1981-1982 and surpassed $4 billion annually by 1983. By 1984, the division's expansion, including XT sales, supported IBM's company-wide revenue climbing to $46 billion, with personal computer shipments more than tripling from prior levels. In the mid-1980s, IBM maintained a 25-30% share of the business market, bolstered by the XT's appeal to enterprises seeking reliable, expandable systems. However, this position eroded as lower-priced clones proliferated, reducing IBM's overall PC from about 80% in 1983 to 38% by 1987. The XT's base price of $4,995 reinforced its enterprise focus but constrained consumer adoption relative to more affordable competitors.

Long-term Impact

The IBM Personal Computer XT played a pivotal role in reinforcing the open (ISA) introduced with the original IBM PC, by providing eight expansion slots that encouraged third-party hardware development and compatibility. This openness enabled the proliferation of IBM-compatible clones from manufacturers like and , which captured over 90% of the PC market by the early 1990s due to lower costs and rapid innovation. By introducing the first built-in (HDD) as a standard feature—a 10 MB Seagate unit—the XT popularized persistent storage in personal computers, shifting the industry from floppy-disk reliance to more efficient data management and application loading. This innovation influenced the design of successors like the PC AT, which integrated faster HDD interfaces, and the PS/2 line, which advanced storage standards while building on XT-era compatibility. Additionally, the XT shipped with PC-DOS 2.0, the first version supporting HDDs and hierarchical file systems, fostering a robust DOS software that powered business applications and games for decades. In contemporary retro computing, the XT remains a foundational platform for enthusiasts, with emulators such as DOSBox-X providing cycle-accurate simulation of its 8088 processor, 360 KB floppy drives, and ISA bus to preserve and run 1980s software. Well-preserved mint-condition XT units, including original peripherals and documentation, command collector values exceeding $500 as of 2025, reflecting their status as artifacts of early PC evolution. As a hallmark of 1980s office computing, the XT symbolized the mainstream adoption of PCs in corporate environments, streamlining operations through tools like and . Its success contributed to IBM's PC division achieving revenue peaks in the mid-1990s—surpassing $20 billion annually—before sustained market pressures led to the division's divestiture to in 2005 for $1.75 billion.

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