DEC Rainbow 100 (1982)

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The DEC Rainbow 100, released in 1982, is a unique beast. It was capable of three different operation modes: VT102 terminal display mode (for using DEC’s line of VAX minicomputers), Z80 (CP/M) mode, and 8088 (MS-DOS) mode. It was not cheap, costing $3,245 for the original 100A model, $2,750 for the revised 100B, and $5,475 for a pre-installed Winchester hard disk drive in the 100B.

The Z80 CPU, clocked at 4MHz, worked in tandem with the 8088 CPU, clocked at 4.8MHz. They shared the same 64KB RAM (100B came with 128KB, both upgradable to 896KB) and did extra hardware controlling work while the other was acting as the primary CPU. It came with a special version of CP/M, called CP/M 80/86, which could run software made both for the 8-bit Z80 CP/M, as well as software written for the 16-bit CP/M-86, without needing to reboot the computer. MS-DOS and Windows 1.0 were later brought to the system, and a third-party hardware upgrade added in a 80286 alongside a modified Windows 3.0.

One notable feature, aside from its inability to display color graphics without addon hardware, is the unique floppy disk drive. Nicknamed the toaster, it uses one motor to drive two disks. The disk in the bottom slot needed to be inserted upside down. Sadly, this unique machine that bridged the CP/M era to the MS-DOS era didn’t sell very well, due to its high price and general apathy from DEC and its vendors.

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