Heath H-100 and Zenith Z-100 The Heath/Zenith Z-100 was a late entry into the S-100 based system area, and followed the then-new IEEE standard for the S-100 bus and cards designed to plug into it. The Z-100 was a dual-processor system, having both an 8085 and an 8088. When using the 8085, the system ran CP/M and when using the 8088 it ran MS-DOS or CP/M-86. It was not completely IBM-compatible, though there were modifications which improved it's compatibility, such as the addition of the 'Gemini' daughtercard to it's motherboard. It was a one piece system with it's attached keyboard. It had 5 S-100 bus slots under it's cover, and two 5-1/4" half-height drive bays, as well as two serial ports, a parallel port, a 9pin digital RGB connector, and a composite video connector on the rear panel, as well as cutouts on the rear of the case for additional ports and such coming off of expansion cards. These machines were quite rugged and were used widely by the military. The machine was also sold under the Heath name as the H-100 series as a kit. Zenith had purchased Heath and it's kits in the late 1970's and sold a number of computers and terminals under both names, one prebuilt as a Zenith system and the other as an unbuilt kit as a Heath system. Otherwise the two were identical.

This example from Zenith has 640k, dual 5-1/4" floppy drives, a Heath floppy controller which supports both 5-1/4" and 8" floppy drives, the Gemini daughter card, and a Zenith monitor. I've run this system using both MS-DOS 2.11 and CP/M-86 1.1. Due to the Gemini daughtercard, when this machine boots up, it goes into a menu which allows you to choose which processor mode you would like to boot into. If you choose to boot from the 8088, it then puts you into the Zenith monitor program where you must then tell it to boot from one of the disk drives. The Z-100 was also available with the monitor integrated into the unit as a single piece. The one described above without the integrated monitor was dubbed the 'low-profile' model. The example from Heath has a single 5-1/4" floppy and the Winchester hard disk option. It also has a ADS Promblaster II EPROM programmer in one of the other S-100 bus slots.

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