IBM PS/2 portable computers
| Company type | Product line |
|---|---|
| Industry | Computer hardware |
| Predecessor | IBM PS/2 |
| Founded | 1989 |
| Products | Portable personal computers (PS/2 P70, PS/2 P75) |
| Owner | IBM |
The IBM PS/2 portables represent a line of Micro Channel architecture-based portable PS/2 systems introduced by IBM in 1989.
PS/2 P70
Debuting in May 1989, the P70 was equipped with an Intel 386 processor running at either 16 or 20 MHz, supported up to 8 MB of RAM through four 72-pin SIMM slots, and offered storage choices including 30, 60, or 120 MB ESDI hard drives. It featured a 10-inch gas plasma screen displaying VGA graphics at 640x480 resolution and weighed around 20.8 pounds. In Japan, this model was sold under the name PS/55 5545-T, maintaining identical technical specifications but incorporating a different keyboard layout.
PS/2 P75
Introduced in November 1990, the P75 was an enhanced successor to the P70 and distinguished itself as the first portable computer in the United States to utilize an Intel 80486 DX-33 CPU. Its design mimicked a briefcase and it required A/C power exclusively, which was common among high-performance portables during that period. The system came with a 10-inch flat gas plasma display capable of 640x480 resolution with support for 16 shades of gray, and featured internal SCSI hard drives available in either 160 MB or 400 MB capacities.
With its advanced hardware for the time, the P75 was capable of functioning as a portable server. Pricing began at US$15,990 and could exceed $18,500 depending on configuration choices. Two variants were offered, differing only in their hard drive size:
- 8573-161 — SCSI hard disk with 160 MB capacity
- 8573-401 — SCSI hard disk with 400 MB capacity
Design
The IBM P75 was engineered with portability in mind, adopting a briefcase-like form factor where all essential components—including the display, floppy disk drive, and keyboard—were securely stored behind the keyboard during transportation. To use the device, it is placed on a flat surface; the keyboard is then unlatched and swings downward, allowing it to be fully detached and adjusted for height. The viewing angle of the screen can be modified using side-mounted tabs. Accessing the floppy drive involves pressing a release mechanism on its cover.
Hardware
While sharing many specifications with IBM's model 90, the IBM P75 was specifically designed as a portable unit. It incorporated an Intel i486-DX running at 33 MHz mounted on a dedicated processor complex card and utilized IBM's Micro Channel architecture (MCA) bus featuring four internal slots: one 32-bit AVE slot, one 32-bit MME slot, and two shorter 16-bit slots.
Its built-in gas plasma panel supported multiple video standards including XGA/VGA, EGA, MCGA, and CGA at a resolution of 640×480 pixels with a palette of 16 gray shades. The display could simultaneously output to both its internal screen and an external monitor; when only an external display was used, it supported resolutions up to 800x600 pixels with 16-bit high color under Windows 95 using third-party drivers.
The full-sized IBM keyboard contained 101 keys and doubled as a protective cover during transport, connecting to the system via a flexible 14-inch rolled-coil cable. Storage options included either a 160 MB or a 400 MB SCSI hard drive, supported by an onboard SCSI controller capable of addressing up to 1 GB.
Memory expansion allowed up to 16 MB through four SIMM slots compatible with IBM-manufactured 2 MB or 4 MB SIMMs rated at 70 nanoseconds; however, non-IBM or generic SIMMs required modification due to "presence detect" circuitry requirements. The default RAM configuration shipped with was typically 8 MB.
Available connectivity ports consisted of external SCSI, parallel, serial interfaces, PS/2 mouse ports, an external connection for a 5.25" floppy drive, and VGA output—all hidden behind a rear access door that also served as storage for the power cable during transport. Power input utilized an IEC C14 connector supporting voltages from 100 to 240 volts at up to 3.0 amps.
Software
Similar to other PS/2 models from the same period, the IBM P75 utilizes reference diskettes to adjust system configurations such as memory allocation, port assignments, and installed hardware options. These configurations are saved within CMOS memory and powered by an internal 6V non-rechargeable battery. Should this battery deteriorate, the system might encounter POST failures caused by corrupted CMOS information. The reference diskette also includes fundamental diagnostic utilities. In the absence of a hard drive or operating system, the P75 defaults to booting IBM Cassette BASIC.
While IBM did not provide a pre-installed operating system, the P75 was fully compatible with OS/2, AIX, MS-DOS, IBM PC DOS, and Microsoft Windows.