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.

North Star Computers

Disk controller and drive

North Star Single Density Disk Controller, Shugart SA-400 Disk Drive and Floating Board Board

In the early days of 8080 eight-bit computers users bought either an Altair or IMSAI S-100 bus computers.  To get them up and running, the user toggled in a bootstrap loader that allowed the user read a BASIC interpreter from either an optical paper tape reader or a cassette tape. After the BASIC interpreter was loaded, you could key in a program.

In 1978 the North Star disk system came to market with was a 5 inch Shugart disk drive that held 89 kilobytes of storage coupled to an S-100 buss controller, cable with North Star DOS and BASIC.  It cost $700.00 in kit form and was the first floppy disk system that was affordable to hobbyists.

The front panel of the computer could be addressed to E800 hex, hit the load then run switch, and within a few seconds the North Star DOS prompt would display, (providing you could understand how to configure your computer system for your terminal or video display card.)  Once you had the DOS prompt, you could run the BASIC interpreter, load a program, save a file and make file calls from the BASIC. It was absolutely Great!

North Star Computers was the brainchild of Drs. Chuck Grant and Mark Greenberg. Their next product was the North Star Horizon which was an S-100 buss computer with two floppy disk drives, (which soon became double density, then double sided) which gave them a capacity of 360 Kbytes per disk drive. Later an 18 megabyte Winchester drive could be added to the parallel port. Though it competed with other computers and the 8 inch disk format, the North Star Horizon was a very popular computer in the era from 1979 to 1985.


After the Horizon came the Advantage and the Dimension.

A few of us were lucky enough to be a part of North Star during that time.

North Star Brochure May 1980