North Star Horizon

North Star Horizon 01 - 800

The NorthStar Horizon was a popular 8-bit S-100 bus computer introduced in October 1977. It was built around the ZiLOG Z80A microprocessor, and ran the North Star DOS, (Disk Operating System)  or the CP/M operating system. It was produced by North Star Computers, and it could be purchased either in kit form or pre-assembled.

The computer consists of an aluminium chassis separated into left and right compartments with a plywood cover which sat on the top and draped over the left and right sides. The rear section of the compartment on the right held a linear power supply, including a large transformer and power capacitors, comprising much of the bulk and weight of the system. The empty section in front of the power supply normally housed one or two floppy disk drives, placed on their side so the slots were vertical. The compartment on the left held the S-100 motherboard, rotated so the slots ran left-right. Although a few logic circuits were on the motherboard, primarily for I/O functions, both the processor and the memory resided in separate daughterboards.

Capable of running CP/M and NSDOS (NorthStar’s proprietary Disk Operating System), a standard NorthStar system sported one or two hard-sectored 5.25 inch floppy disk drives and a serial interface to which one could connect a terminal to interact with it. NSDOS included NorthStar BASIC which differentiated from Microsoft in one major way in that North Star BASIC uses BCD numerical calculations whereas Microsoft BASIC uses binary calculation which yield less accuracy.

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