IBM 5100 Portable Computer
The IBM 5100 Portable Computer was a desktop computer introduced in September 1975, six years before the IBM PC. It was the evolution of a prototype called the SCAMP (Special Computer APL Machine Portable) that IBM demonstrated in 1973. In January 1978 IBM announced the IBM 5110, its larger cousin. The 5100 was withdrawn in March 1982.
When the PC was introduced in 1981, it was originally designated as the IBM 5150, putting it in the “5100″ series, though its architecture wasn’t directly descended from the IBM 5100.
Description
The IBM 5100 is based on a 16-bit processor module called PALM (Put All Logic in Microcode). The IBM 5100 Maintenance Information Manual also referred to the PALM module as the controller. PALM can directly address 64 KB of memory. Some configurations of the IBM 5100 had Executable ROS (ROM) and RAM memory totaling more than 64 KB, so a simple bank switching scheme was used. The actual APL and/or BASIC interpreters were stored in a separate Language ROS address space which the PALM treats as a peripheral device.
The portable computer
A single integrated unit provided the keyboard, five-inch CRT display, tape drive, processor, several hundred kilobytes of read only memory containing system software, and up to 64 KB of random access memory. It was the size of a small suitcase, weighed about 55 lb (25 kg), and could be transported in an optional carrying case, hence the “portable” moniker.
While the IBM 5100 seems large today, in 1975 it was an amazing technical accomplishment to package a complete computer with a large amount of ROM and RAM, CRT display, and a tape drive into a machine that small; it was two more years before the similar Commodore PET was released. Earlier desktop computers of approximately the same size, such as the HP 9830, did not include a CRT nor nearly as much memory. An equivalent late-1960’s IBM computer would have been nearly as large as two desks and would have weighed about half a ton.
External monitor
An external video monitor (or modified television receiver) could be connected to the IBM 5100 via a BNC connector on the back panel. While the 5100 had a front panel switch to select between white on black or black on white for the internal display, this switch did not affect the external monitor, which only offered bright characters on a black blackground. The vertical scan rate was fixed at 60 Hz, which may have been inconvenient for users in countries using 50 Hz broadcast television systems (e.g., many European and South American countries).
Communications adapter
Also in September 1975 IBM announced the IBM 5100 Communications Adapter. That allowed the 5100 to transmit data to and receive data from a remote system. It made the 5100 appear the same as an IBM 2741 Communications Terminal and in theory was able to communicate with IBM 2741 compatible machines in start-stop mode using the EBCD (Extended Binary Coded Decimal) notation. EBCD was similar to the more common IBM EBCDIC code, but not identical.
Research Device Coupler
In Volume 16, Number 1, Page 41 (1977) of the IBM Systems Journal the article “The IBM 5100 and the Research Device Coupler — A personal laboratory automation system” read: “A small laboratory automation system has been developed by using the IBM 5100 Portable Computer in conjunction with the Research Device Coupler. This compact system provides a dedicated, high-level-language computer and a versatile data acquisition and control interface for experiments in which data rates do not exceed 9600 Baud. Two experiments exemplify the use of the system. The Research Device Coupler described in this paper is a prototype of the IBM 7406 Device Coupler.”
Different models
Available in 12 models providing 16 KB, 32 KB, 48 KB or 64 KB of main storage, the 5100 sold for between $8,975 and $19,975.