Ohio Scientific

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Ohio Scientific was a computer company that built and marketed computers from the late 1970's to the early 1980's.

One of their first products, launched in 1978 was the OSI Model 500 system, a very simple single board computer based on the MOS Technology 6502 microprocessor, but lacking a Video Display Controller. It needed an external video terminal such as the VT100, or the CT-64 terminal system from SWTPC, to create a useful system. Their later products were also 6502-based, the Superboard II, Challenger 1P, Challenger 4P and Challenger 8P, introduced in 1979 and discontinued in 1981.

Original Ohio Scientific motherboard designs used 7400-series transistor-transistor logic TTL chips. Instead of using a floppy-disk controller IC, they used the Motorola 6850 ACIA serial-port UART chip, which made their 8 and 5 inch floppies unreadable on any other system.

The company supplied full schematics of their hardware,which allowed for some field modifications such as increased clock speed, and increased video line length.

The video systems did not have color-graphics like the Apple II, just upper-case text, and some pseudo graphical characters, (comparable to the "PETSCII" character-set of the Commodore PET) for drawing lines and supporting simple games. They hadn't figured out how to write to the video memory without glitching the display, so the hardware would blank the screen for a few microseconds while it accessed the video memory. There was an add-on graphics card for the Superboard that would display 256 by 256 pixels. It came with software to draw 3D graphics.

The software was also very minimalist. A cassette boot loader in ROM and Microsoft BASIC in ROM. Disk-based systems included a bare-bones "Disk Operating System", which did not have file names, only disk track numbers. Users were advised to reserve track 40 as a text area for a manual disk directory. Even so, the disk was being much handier than reading and writing cassettes at 1200 baud.