Rainbow 100

from Wikipedia, the free encyclopedia
DEC Rainbow 100

Rainbow 100 was a microcomputer that was introduced by Digital Equipment Corporation (DEC) in May 1982, but actually wasn't available in quantities until a few months later. As a special feature, he had both an 8-bit and a 16 bit - CPU . The hardware also included the functionality of a VT100 terminal. The special focus on ergonomics was also unusual for the time .


The Rainbow 100 was equipped with two CPUs, a Zilog Z80A , clocked at 4 MHz , and an Intel 8088 (4.8 MHz). The central unit had 64 kB RAM as standard , upgradeable to 128 or 256 kB, as well as 24 kB ROM for self-diagnosis, start routines, terminal software and service functions. On the rear of the housing there were serial interfaces for communication and printer as well as the connection for the screen . A double floppy disk drive, type RX50, for 5.25 ″ floppy disks with double density on 80 tracks with 10 sectors and 409 kB storage capacity was installed as standard in the Rainbow 100 . This could also read and write floppy disks in the VT180 format. An RS422 interface enabled a hard disk subsystem with a capacity of 5 MB to be connected. The computer could be switched to terminal mode. The device could not only process 8-bit and 16-bit software as a computer, but could also be used as a "stupid" screen terminal (VT102) on mainframes.

The monochrome screen was connected to the system unit by cable, the keyboard in turn to the screen. The anti-reflective screen was available in three color variants of the character display, black and white, green and amber yellow. The characters were displayed in a 7 × 9 matrix on 24 lines with 80 or optionally 132 characters. The character attributes, flashing, underlined, bold, inverted as well as double character height and width were available. In addition, the screen could be switched from light characters on a dark background to dark characters on a light background.

Bit pattern graphics for resolutions of 800 × 240 pixels with four colors or 384 × 240 pixels with 16 colors required an additional plug-in card with an NEC µPD7220 controller and an additional monitor.

Operating systems

As standard, the Rainbow 100 was equipped with a special version of the CP / M operating system, which was designated as CP / M-86/80. It had a "Softsense" facility that automatically recognized 8 or 16 bit software in order to then automatically assign it to the appropriate processor. The system supported both the 20 system functions of the CP / M-86 for 16-bit software and the 17 CP / M-80 functions.

In addition, MS-DOS was offered, which, however, was not compatible with IBM due to its hardware .


IBM Model M, from 1985, with enhanced 101-key layout

The focus on ergonomics is a special feature of the time. The structure of the housing of the central unit allowed it to be dismantled into the individual modules without tools. Although the monitor was only the usual size of 12 inches at the time, it had an excellent anti-reflective coating and displayed the characters with particular clarity and sharpness. In addition, an automatic screen switch-off after 30 minutes was included as a screen saver .

The keyboard of the Rainbow 100 with 104 keys in four functional areas (keypad, cursor keys , numeric keypad and function keys ) already largely anticipated the ergonomic layout , which was only introduced later by IBM with the Model M and which has been preserved to this day.

The basic settings of the Rainbow via the special procedure via the “SET-UP” button contain help functions. With the LEARN program on diskette, a simple e-learning function was available for the system.

The Rainbow 100 received the iF product design award 1984 for its ergonomic design .


In addition to the hard disk subsystem (via RS422 port), DEC offered two matrix printers and a print wheel printer that could be operated on the serial RS-232 interface. The Rainbow 100 did not have a parallel interface for printers.


The first version was also known as "Rainbow 100A". In 1984 DEC launched the “Rainbow 100+” model. This was largely identical to the previous model, but the new features were a 10 MB hard disk drive and the expandability of the main memory up to 896 kB.

Market success

The Rainbow 100 did not achieve the expected market success. The devices and other components were relatively expensive. For example, the basic system with printer cost 14,000 DM in 1983 alone. Due to its construction with two CPUs, the computer was generally well equipped for CP / M software, but with CP / M software, above all, system input and output had to be adapted to the hardware become. Both internationally and in Germany, there was little software specifically for the Rainbow 100.

The market had already started to orient itself towards IBM compatibility. DEC could not keep up here, especially since the hardware interrupts in the basic construction of the Rainbow 100 were not matched to the software interrupts of MS-DOS.


  • Magazine Computer Personal , No. 9, April 1983, p. 108 ff., DEC Rainbow 100 - the versatile one
  • Chip magazine , No. 6, June 1983, p. 64 ff., Test: DEC Rainbow 100
  • Chip magazine, No. 4, April 1984, pp. 288 ff., Test: DEC Rainbow 100+

Web links

Individual evidence

  1. ifdesign.de: iF product design award 1984. Accessed December 21, 2014 .