North Star Homebrew S-100

North Star Homebrew S-100

[Vin167]

North Star Computers pioneered the first affordable floppy disk system for S-100 bus homebrew computers in 1976-1977, revolutionizing data storage for hobbyists who previously relied on unreliable paper tape and cassette systems, their $700 kit-form Micro-Disk System with proprietary hard-sectored format, DOS, and BASIC made persistent storage accessible to the Homebrew Computer Club generation and became wildly successful in the early microcomputer market. The company later produced the iconic North Star Horizon (1978), one of the first complete S-100 systems with integrated floppy drives in a distinctive wooden case, which could run CP/M or their proprietary NSDOS and became a cornerstone platform for small business computing before the IBM PC era. Homebrew computing was critically significant in early computing history because it democratized computer access beyond corporate and academic institutions, hobbyists building S-100 systems in garages and collaborating through clubs like the Homebrew Computer Club drove innovation through cost reduction, open sharing of designs and software, and the do-it-yourself ethos that transformed computing from expensive mainframes into affordable personal machines, directly spawning the first personal computer startups and establishing industry practices still relevant today.

• Manufacturer: North Star Computers
• Type: Personal Computer
• Release Date: 1978
• Cost at release: CAD ~$3,650 (adjusted for inflation)
• Cost with peripherals: CAD ~$15,000 (adjusted for inflation)
• MIPS: 0.05 (50 KIPS)

Hardware Specifications

• CPU: Zilog Z-80 CPU running at 4 MHz
• Memory: Typically 16K to 64K RAM (varies by configuration)
• Storage: Originally included one or two 5.25″ single-sided, double-density floppy disk drives (360K capacity each), with an optional 5 MB Winchester hard disk
• Motherboard: 10 to 12-slot S-100 backplane with built-in circuitry for port I/O
• I/O: Two RS-232 serial ports, one 8-bit parallel port; supports printer, terminals, modems
• Disk Controller: Integrated S-100 bus floppy disk controller

Operating System & Programming Languages 

• Operating System: The North Star Homebrew S-100 ran primarily two operating systems:
  • North Star’s own proprietary operating system called HDOS (also referenced as NSDOS or NorthStar DOS)
  • CP/M (Control Program for Microcomputers), a popular OS for S-100 bus machines
• Supported Languages: NorthStar BASIC (including a version called Floating Point BASIC). Programs written for CP/M which supported many languages like BASIC, assembly, COBOL, FORTRAN, and others depending on user-installed software

Notables

• It was among the first to popularize floppy disk storage with its integrated disk controller, offering 5.25″ floppy drives when many contemporaries relied on cassette storage.
• North Star DOS (HDOS) was a pioneering easy-to-use disk operating system before CP/M dominance.
• The system used the Zilog Z-80 CPU, which was a leading processor in early microcomputers.
• Nicknamed among hobbyists and early adopters as a “Homebrew” system due to its popularity in hands-on assembly and customization.
• It helped establish the S-100 bus as a standard for early microcomputer expansion and compatibility.
• North Star’s floppy disk controller was regarded as more reliable than early competition, boosting the system’s reputation for data storage.
• It was considered a high-quality, expandable, and practical system bridging hobbyist computing and professional use.
• Classic advertisements emphasized “North Star’s Advantage is easy to see,” highlighting disk storage and operating system ease.
• It contributed significantly to the transition from kit computers to commercial personal computers with expandability and disk-based OS.

Donated by: Dr. Arlen Michaels