IBM PS/1

The PS/1 is a brand for a line of personal computers that marked 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.

Position among IBM's PC brands

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. American PS/1 models came with a modem installed so users could access online IBM help services, which were provided by partnerships with Prodigy and Quantum Computer Services.
Like the PCjr, the PS/1's name suggested a more limited machine than IBM's business line, the PS/2. However, unlike the PS/2, the PS/1 was based upon architecture closer to the AT and compatibles, for example using ISA, plain VGA, and IDE. Although the first models used custom-designed components and design, later desktop and tower models used mostly standard components. The earlier models included a ROM with IBM's PC DOS and a graphical shell, however the system was compatible with other DOS implementations and the shell could be installed on the hard drive. 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. There were several form factors used during the PS/1's production, with the 2133 and 2155 cases used for several model years, while the 2168 tower case was offered later in later models of the PS/1 lineup:

2011 Proprietary design, power supply is within CRT
2121 Proprietary design, power supply is within CRT, up to two available ISA slots
2123 Limited-production model. Based on IBM PS/2 model 30 case, three available ISA slots
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, including a 5.25" bay.
2168 Tower unit. The 6x8 references the available slots and bays, including 5.25" bays.

Models

Models 2011

The original PS/1, based on a 10 MHz Intel 80286 CPU, was designed to be easy to set up and use. It featured 512 KB or 1 MB of on-board memory, built-in modem and an optional 30 MB hard disk. Later models had an optional 40 MB hard disk. IBM also released a 5.25" disk drive unit, a $169 expansion box called Adapter Card Unit that could hold three 8/16 bit ISA third-party expansion cards. A $995 CD-ROM drive, based on a Western Digital SCSI chip, could be fitted underneath the case. The first generation of PS/1 models suffered from very limited expansion capabilities, since they lacked standard ISA expansion slots, unless you bought the expansion box. You could however add up to three $199 512 Kb memory cards, that was easy to install. The original offering was 4 models:

$999 VGA Mono, 512 Kb RAM
$1.499 VGA Color, 512 Kb RAM
$1.699 VGA Mono, 1 Mb RAM, 30 Mb hard disk
$1.999 VGA Color, 1 Mb RAM, 30 Mb hard disk

Model 2121

The 2121 series computers used the same form factor as the 2011 series, but included up to two ISA slots inside the case. Memory could be expanded from 2 MB to 6 MB using a proprietary 4 MB memory module. The higher-end 2121 featured an Intel 80386SX processor running at 16 or 20 MHz.
The 2121 series PS/1 computers can be split into the following major hardware categories:

Model	US List	MB FRU	CPU	ISA Slots	RAM	VRAM	Hard-Drive	Serial / Modem
2121-C42	$1,699	92F9690	Intel 80386SX @ 16 MHz	0	2 MB	256 KB	95F4720	2400 baud modem
2121-B82	$2,199	92F9690	Intel 80386SX @ 16 MHz	2	2 MB	256 KB	92F9943	2400 baud modem
2121-C92	?	?	Intel 80386SX @ 16 MHz	0	2 MB	256 KB	129 MB IDE	2400 baud modem
2121-NE3	?	92F9673	Intel 80386SX @ 16 MHz	2	?	?	95F4722	2400 baud modem
2121-G42	?	93F2184	Intel 80386SX @ 20 MHz	0	2 MB	256 KB	40 MB IDE	2400 baud modem
2121-A82	?	?	Intel 80386SX @ 20 MHz	2	2 MB	256 KB	40 MB IDE	2400 baud modem
2121-S92	?	?	Intel 80386SX @ 20 MHz	0	2 MB	256 KB	129 MB IDE	2400 baud modem
2121-M82	?	?	Intel 80386SX @ 20 MHz	2	2 MB	256 KB	80 MB IDE	2400 baud modem
2121-A62	?	?	?	2	?	256 KB	56F8863	2400 baud modem
2121-A92	?	?	?	?	?	256 KB	IDE	serial port
2121-A94	?	?	Intel 80386SX @ 20 MHz	2	6 MB	256 KB	129 MB IDE	2400 baud modem

Monitors:
IBM made the decision to put the DC power supply in the monitor, making use of third-party monitors difficult and essentially impractical and limiting the usefulness of the computer if the monitor needed service. Some models were sold with greyscale VGA monitors. However, some hobbyists could manage to remap the pinouts to allow for third-party monitors.
"DOS in ROM”:
Similar to a few Tandy 1000 models, the early 2011 and 2121 had an operating system built into ROM, rather than loading it from a hard drive. The ROM disk would then load a "4-quad" screen which allowed users to access help, rapidly launch pre-installed software, connect online, and access files on the hard drive. It was possible to have the computer boot from the hard drive if the operating system was upgraded, and IBM provided a DOS 6.22-compatible version of the "4-quad" program that could be launched from the hard drive if users wished to continue using it.

Model 2133

The 2133 series PS/1 computers can be split into the following major hardware categories:

Model	MB FRU	CPU	RAM	SIMM	Video chip	VRAM	Hard-Drive	Notes
2133-111	32G1768	Intel 80386SX @ 25 MHz	2 MB	2×72 Pin FPM	Cirrus CL-GD5410	256 KB	95F7173
2133-711	93F2397	Intel 80386SX @ 25 MHz	2 MB	2×72 Pin FPM	Cirrus CL-GD5410	256 KB	59G9567
2133-811		Intel 80386SX @ 25 MHz	4 MB				85 MB IDE
2133-13	?	Intel 80386SX @ 25 MHz	2 MB	2x72 Pin FPM		256 KB	?
2133-W13		Intel 80386SX @ 25 MHz	2 MB				129 MB IDE
2133-13T	65G3766	Intel 80486SX @ 25 MHz	4 MB	2×72 Pin FPM		256 KB	93F2329
2133-?43	34G1885	Intel 80486SX @ 20 MHz	4 MB	2×30 Pin FPM		512 KB	93F2329
2133-?50	34G1848	Intel 80486SX @ 25 MHz	4 MB	2×30 Pin FPM		512 KB	93F2329
2133-?53	34G1848	Intel 80486SX @ 25 MHz	4 MB	2×30 Pin FPM		512 KB	93F2329
2133-652		Intel 80486SX @ 33 MHz	4 MB	4×72 Pin FPM	Cirrus CL-GD5424	512KB	84G3927
2133-575		Intel 80486DX @ 33 MHz	4 MB	4×72 Pin FPM		512 KB	170 MB IDE
2133-594		Intel 80486DX2 @ 66 MHz	4 MB	4×72 Pin FPM		512 KB	253 MB IDE
2133-E11		Intel 80386SX @ 25 MHz	2 MB	2×72 Pin FPM	Cirrus CL-GD5424	512 KB	85 MB IDE	Canada models, English model
2133-F11		Intel 80386SX @ 25 MHz	2 MB	2×72 Pin FPM	Cirrus CL-GD5424	512 KB	85 MB IDE	Canada models, French model
2133-E43		Intel 80486SX @ 20 MHz	2 MB	8×30 Pin FPM	Tseng ET4000	512 KB	129 MB IDE	Canada models, English model
2133-F43		Intel 80486SX @ 20 MHz	2 MB	8×30 Pin FPM	Tseng ET4000	512 KB	129 MB IDE	Canada models, French model
2133-E53		Intel 80486SX @ 25 MHz	2 MB	8×30 Pin FPM	Tseng ET4000	512 KB	129 MB IDE	Canada models, English model
2133-F53		Intel 80486SX @ 25 MHz	2 MB	8×30 Pin FPM	Tseng ET4000	512 KB	129 MB IDE	Canada models, French model

Model 2168

European models

Model	MB FRU	CPU	RAM	Video chip	VRAM	Hard-Drive	Notes
2168-452		Intel 80486SX @ 25 MHz	2 MB			85 MB IDE
2168-463		Intel 80486SX @ 33 MHz	4 MB			130 MB IDE
2168-473		Intel 80486DX @ 33 MHz	4 MB			130 MB IDE
2168-483		Intel 80486DX @ 50 MHz	4 MB			129 MB IDE
2168-493		Intel 80486DX2 @ 66 MHz	4 MB			130 MB IDE
2168-552		Intel 80486SX @ 25 MHz	4 MB			129 MB IDE
2168-584		Intel 80486DX2 @ 50 MHz	4 MB			253 MB IDE
2168-594		Intel 80486DX2 @ 66 MHz	4 MB			253 MB IDE

US models

Model	MB FRU	CPU	RAM	Video chip	VRAM	Hard-Drive	Notes
2168-BB1		Intel 80486DX2 @ 66 MHz	4 MB	CL-5428	1 MB	420 MB IDE
2168-US1		Intel 80486DX2 @ 50 MHz	4 MB	CL-5428	1 MB	340 MB IDE
2168-SR1		Intel 80486SX @ 33 MHz	4 MB	CL-5428	1 MB	253 MB IDE
2168-38C		Intel 80486DX2 @ 50 MHz	4 MB	CL-5428	512 KB	340 MB IDE
2168-57C		Intel 80486DX2 @ 66 MHz	8 MB	CL-5428	1 MB	720 MB IDE
2168-37C 2168-33T 2168-31E		Intel 80486DX2 @ 50 MHz	4 MB	CL-5428	512KB	253 MB IDE
2168-56C 2168-54T 2168-51E		Intel 80486DX2 @ 66 MHz	8 MB	CL-5428	1 MB	420 MB IDE
2168-28V		Intel 80486SX @ 33 MHz	4 MB	CL-5428	512 KB	253 MB IDE
2168-58V		Intel 80486DX2 @ 66 MHz	8 MB	CL-5428	1 MB	420 MB IDE
2168-G57 2168-S55 2168-W52		Intel 80486SX @ 33 MHz	4 MB	CL-5426	1 MB	170 MB IDE
2168-G87 2168-S85 2168-W82		Intel 80486DX2 @ 66 MHz	4 MB	CL-5426	1 MB	250 MB IDE
2168-P89		Intel 80486DX2 @ 66 MHz	4 MB	CL-5426	1 MB	340 MB IDE	-

Post-"DOS in ROM" models

On May 11, 1993, IBM introduced a "new generation" of the PS/1 line. Later PS/1s featured standard LPX-architecture motherboard. Many of these later PS/1s shipped from the factory with MS-DOS and Microsoft Windows, rather than IBM's PC DOS 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.

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.