# IBM PS/1

The PS/1 (known in some European countries as the PS/1000$^{:95}$) 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.
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 (Model 2011), 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 (expandable to 2.5 MB with proprietary memory modules), built-in modem (in American models only) 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 (ACU) 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 (ACU). 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 (640x480), 512 Kb RAM
* $1.499 VGA Color (640x480), 512 Kb RAM
* $1.699 VGA Mono (640x480), 1 Mb RAM, 30 Mb hard disk
* $1.999 VGA Color (640x480), 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 (40 MB IDE) | 2400 baud modem |
| 2121-B82 | $2,199 | 92F9690 | Intel 80386SX @ 16 MHz | 2 | 2 MB | 256 KB | 92F9943 (80 MB IDE) | 2400 baud modem |
| 2121-C92 | ? | ? | Intel 80386SX @ 16 MHz | 0 | 2 MB | 256 KB | 129 MB IDE | 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 (160 MB IDE) | 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 (similar to the problems of the Coleco Adam and Amstrad 1512 years earlier). 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 (PC DOS 4.01) 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 (80 MB IDE) | |
| 2133-711 | 93F2397 | Intel 80386SX @ 25 MHz | 2 MB | 2×72 Pin FPM | Cirrus CL-GD5410 | 256 KB | 59G9567 (85 MB IDE) | |
| 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 (129 MB IDE) | |
| 2133-?43 | 34G1885 | Intel 80486SX @ 20 MHz | 4 MB | 2×30 Pin FPM | | 512 KB | 93F2329 (129 MB IDE) | |
| 2133-?50 | 34G1848 | Intel 80486SX @ 25 MHz | 4 MB | 2×30 Pin FPM | | 512 KB | 93F2329 (129 MB IDE) | |
| 2133-?53 | 34G1848 | Intel 80486SX @ 25 MHz | 4 MB | 2×30 Pin FPM | | 512 KB | 93F2329 (129 MB IDE) | |
| 2133-652 | | Intel 80486SX @ 33 MHz | 4 MB | 4×72 Pin FPM | Cirrus CL-GD5424 | 512KB | 84G3927 (171 MB IDE) | |
| 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 | CPU | RAM | Hard-Drive |
| 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 80386DX @ 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 | CPU | RAM | Video chip | VRAM | Hard-Drive |
| 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 (Consultant) 2168-33T (Expert) 2168-31E (Essential) | Intel 80486DX2 @ 50 MHz | 4 MB | CL-5428 | 512KB | 253 MB IDE |
| 2168-56C (Consultant) 2168-54T (Expert) 2168-51E (Essential) | Intel 80486DX2 @ 66 MHz | 8 MB | CL-5428 | 1 MB | 420 MB IDE |
| 2168-28V (Investor) | Intel 80486SX @ 33 MHz | 4 MB | CL-5428 | 512 KB | 253 MB IDE |
| 2168-58V (Investor) | Intel 80486DX2 @ 66 MHz | 8 MB | CL-5428 | 1 MB | 420 MB IDE |
| 2168-G57 (Consultant) 2168-S55 (Expert) 2168-W52 (Essential) | Intel 80486SX @ 33 MHz | 4 MB | CL-5426 | 1 MB | 170 MB IDE |
| 2168-G87 (Consultant) 2168-S85 (Expert) 2168-W82 (Essential) | Intel 80486DX2 @ 66 MHz | 4 MB | CL-5426 | 1 MB | 250 MB IDE |
| 2168-P89 (Investor) | 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.

## Timeline

* Timeline of the IBM Personal Computer vte
* Asterisk (*) denotes a model released in Japan only