Zenith Z89

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Heathkit H-89 aka Zenith Z-89. This unit has two half-height DD diskette drives in place of the single full-height original.

The Z-89 was a personal computer produced by Zenith Data Systems in the early 1980s. It was based on the Zilog Z80 microprocessor and ran the HDOS and CP/M operating systems. The Z-89 was integrated in a terminal-like enclosure with a non-detachable keyboard, 12-inch black/white CRT, hard-sectored controller, and a 5.25" diskette drive. In 1979, prior to Zenith's purchase of Heathkit, Heathkit had originally designed and marketed this computer in kit form as the H89, assembled as the WH89, and without the floppy but with a cassette interface card as the H88. (Note: Prior to the Zenith purchase, the Heathkit model numbers did not include the - 'dash')

Heath/Zenith also made a serial terminal, the H/Z-19, based on the same enclosure (with a blank cover over the diskette drive cut-out) and terminal controller. They even offered an upgrade kit to convert the terminal into a full H/Z-89 computer.

Another configuration, the Z-90, changed the floppy drive controller from the hard-sectored controller (max 100 kB) to a soft-sectored controller that supported double-sided, double density, 96 tpi drives with a capacity of 640 KiB. It also came standard with 64 KiB of RAM.

There were several external drive systems available for the H/Z-89.

The H/Z-77 and H/Z-87 supported up to two additional Single-Sided, Single Density, 48 tpi 5.25" drives. When connected to the standard hard-sectored controller, it could store 100 kB each. By connecting it to a soft-sectored controller, they could store 160 kB.
The H/Z-37 supported up to two Double-Sided, Double Density, 96 tpi 5.25" drives and required the soft-sectored controller. These drives had a capacity of 640 KiB each.
The Z-47 supported two 8" floppy drives and required its own controller. These used the standard IBM 3740 floppy disks.
The Z-67 was a 10 MB Winchester Drive plus one 8" floppy drive and also required its own controller.

A maximum of two disk controller cards could be installed in a standard system.

[edit] Summary

Year	1979 – 1993
CPU	Two Z80, 2 MHz (one for terminal)
RAM	16 KiB – 48 KiB on main board, extra 16 KiB memory card for CP/M (64 KiB total)
Display	integral 12" b/w CRT, 80 × 25 characters (25th line was a special status line)
Storage	5.25" diskette drive (originally hard-sectored, 100 kB)
Interfaces	3 serial, 1 Centronics parallel(optional), external diskette drive connector
Operating System	HDOS, CP/M, or MP/M
Price	Kit version with 1 floppy drive: $1,800 in 1979 = approx. $4,800 in 2005^[1]