IBM PS/1

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The IBM PS/1 personal computer was IBM's return to the home market in 1990, five years after the IBM PCjr. It was replaced by the IBM Aptiva in September 1994. All PS/1 and Aptiva models included modems for accessing online help as well as preloaded software.

1 Position in IBM's PC brands
2 "DOS in ROM" models
3 Post "DOS in ROM" models
4 Discontinuation
5 See also
6 References

[edit] Position in IBM's PC brands

Like the PCjr, the PS/1's name suggested a more limited machine than IBM's business line, the PS/2. However, the PS/1 had a higher degree of compatibility with IBM's business computers. The PS/1 line was created for new computer users and was sold in consumer electronics stores alongside comparable offerings from Compaq, Hewlett-Packard, Packard Bell, and others. All PS/1 models came with a modem installed so users could access online IBM help services. Although the first models were proprietary, later desktop and tower models used mostly standard components. Later models included a feature called "Rapid Resume" which gave the computers the ability to go into standby mode as well as a hibernation function. A unique fact about all PS/1 models is that if one presses and holds both mouse buttons down, powers on the computer and then lets the mouse buttons go when the computer completes its POST, the system resets its BIOS back to original settings^{[citation needed]}. On the 2011 and 2121 series, this reset process would force the unit to boot from the DOS in ROM, rather than off the hard drive. There were several form factors used during the PS/1's production. 2011 Proprietary design, power supply is within CRT 2121 Proprietary design, power supply is within CRT, one available ISA slot 2123 Limited production model. Based on IBM PS/2 model 30 case. 2133 Desktop case. The 3x3 references the available slots and drive bays. 2155 Desktop case larger than 2133. The 5x5 references the available slots and drive bays. 2168 Tower unit. The 6x8 references the available slots and bays.

The 2133 and 2155 cases were used in several model years with the 2168 tower unit appearing a bit later.

An IBM Personal System 1 model 2011

[edit] "DOS in ROM" models

IBM PS/1 (model 2011)
Type	Personal computer
Released	(1990)
Discontinued	(unknown)
Processor	Intel 80286 @ 10 MHz
Memory	1 MB ~ 2 MB
Operating system	PC-DOS 4.01 (in ROM)

The original PS/1, based on a 10 MHz Intel 80286 CPU, was designed to be easy to set up and use. IBM made the unusual decision to put the motherboard and other electronics of the unit in the monitor, making use of third-party monitors impossible and limiting the usefulness of the computer if the monitor needed service (similar to the problems of the Coleco Adam years earlier). The Amstrad PC1512 and PC1640 are examples of PCs that also had their electronics in the monitor. The early 2011 and 2121 series would boot up off the DOS in ROM and load a "4-quad" screen which allowed users to access help, connect online and access files on the hard drive.

It featured 1 MB of memory, built-in modem, an optional 30 MB hard disk, and optional sound card^[1]. IBM also released a 5.25" disk drive unit and an Adapter Card Unit (ACU) to install third-party expansion cards.^{[citation needed]}

IBM PS/1 (model 2121)
Type	Personal computer
Released	(1992)
Discontinued	(1993)
Processor	Intel 80386SX @ 16 MHz
Memory	2 MB ~ 6 MB
Operating system	PC-DOS 4.01 (in ROM)

The 2121 series PS/1 computers used the same form factor as the 2011 series, but included one ISA slot inside the case. Memory could be expanded from 2meg to 6meg using a proprietary 4 megabyte memory module.

IBM PS/1 (model 2155)
Type	Personal computer
Released	(unknown)
Discontinued	(unknown)
Processor	Intel 80486SX @ 25 MHz
Memory	2 MB ~ 6 MB
Operating system	IBM-DOS / Windows 3.1

A later revision featured an Intel 80386SX processor running at 16 MHz.^{[citation needed]}

An Intel 80486SX processor version was released running at 20 MHz. This revision had its own power supply built into the case.

The first PS/1 (2011,2121,2123) models suffered from very limited expansion capabilities, since they lacked standard ISA expansion slots. Similar to a few Tandy 1000 models, the early PS/1's had an operating system (PC-DOS 4.01) built in to ROM, rather than loading it from a hard drive. It was possible to have the computer boot from the hard drive if the operating system was upgraded.

[edit] Post "DOS in ROM" models

On May 11, 1993 IBM introduced a "new generation" of the PS/1 line.[1]

Later PS/1s featured standard LPX-architecture motherboard.

Ironically, many of these later PS/1s shipped from the factory with MS-DOS and Microsoft Windows, rather than IBM's PC-DOS and/or OS/2. An early 2133 model did come preloaded with OS/2 2.1.

This was because IBM targeted OS/2 for high-end computing machines with more power.

[edit] Discontinuation

The PS/1 line was discontinued in 1994 and replaced with the Aptiva line, which was architecturally very similar to the later models of the PS/1, but with a more marketing-friendly name. Aptivas were sold in the United States until early 2000, when price pressures made the line unprofitable and IBM withdrew from the retail desktop PC market entirely.