North Star Horizon

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NorthStar Horizon front placard.jpg
NorthStar Horizon.jpg
A North Star Horizon computer
ManufacturerNorth Star Computers
TypePersonal computer
Release dateNovember 1977; 45 years ago (1977-11)
Introductory price
  • $1899 Assembled
  • $1599 as a Kit
DiscontinuedEarly 1980s
Units sold10,000-100,000+
Operating systemCP/M, NorthStar DOS
CPUZ80 @ 4MHz
Memory16K or more
Storage5.25 floppy drive(s) holds 90KB each
Display80 x 24 text mode
GraphicsRS-232 port
PowerIntegrated 250W P.S.U.
Dimensions50.8 x 44.4 x 18.4 cm
Mass20 kg
SuccessorNorth Star Advantage

The North Star Horizon was a popular 8-bit S-100 bus computer introduced in October 1977.[1][2][3] Like most S-100 machines of the era, it was built around the Zilog Z80A microprocessor, and typically ran the CP/M operating system. It was produced by North Star Computers, and it could be purchased either in kit form or pre-assembled.[4] The North Star Horizon was one of the first computers to have built in floppy drives [5] as well as being one of the first personal computers to have a hard disk drive.[6]

A Z80 processor board for the NorthStar Horizon
An inside view of the NorthStar Horizon


The computer consists of a thick 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. (It is one of only a handful of computers to be sold in a wooden cabinet. Later versions featured an all-metal case which met safety standards.[5]) 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.[citation needed]

Capable of running CP/M and NSDOS (North Star's proprietary Disk Operating System), a standard North Star 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 North Star BASIC, a slightly non-standard dialect of BASIC, where some standard BASIC commands of the day had been changed, probably to avoid potential legal issues. Two examples of this were the EXAM and FILL commands, which took the place of the more common PEEK and POKE.

The Horizon was superseded by the all-in-one North Star Advantage in 1982.[7] The Horizon found a niche in University environments where its inbuilt S-100 bus could be used to interface it to a variety of control systems.[8]

North Star released a hard disk version, with an internal full height 5MB MFM drive. They also released an S-100 card with integrated memory and two serial ports which allowed up to eight users on one Horizon, each with their own CPU sharing the disk and other resources. This operated under TurboDOS, a multi user CP/M variant with some Unix-like features.


  1. ^ North Star Computer Catalogs (PDF). North Star Computer. 1979.
  2. ^ "S-100 Bus / IEEE-696 Archive: North Star Computers Manuals". Retrieved 2022-11-26.
  3. ^ "NorthStar Horizon computer". Retrieved 2022-11-26.
  4. ^ "Horizon, The Complete Computer". Byte. Peterborough NH: Green Publishing. 2 (10): 21. October 1977. The introductory advertisement for the North Star Horizon computer. The price for a Z80 CPU, 16K of RAM and a single floppy drive was $1599 kit and $1899 assembled. Dual drive systems were $1999 kit and $2349 assembled.
  5. ^ a b "NorthStar Horizon computer". Retrieved 26 July 2016.
  6. ^ "NorthStar Horizon Personal Computer". National Museum of American History. Retrieved 26 July 2016.
  7. ^ "OLD-COMPUTERS.COM : The Museum". Retrieved 26 July 2016.
  8. ^ "S100 Computers - NorthStar".

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