Ohio Scientific

Ohio Scientific Inc. (also known as Ohio Scientific Instruments) was a United States computer company that built and marketed microcomputers from 1975 to 1981. Their best-known products were the Challenger series of microcomputers, but they also sold a variety of computer kits, single-board computers and various peripherals.

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. It needed an external computer terminal such as the VT100, Hazeltine 1420, or the CT-64 terminal system from SWTPC, as it lacked an internal video controller.

The Challenger III, introduced in August 1977, had a maximum of 53KB of static ram and used 8" 370k byte floppy disks in its dual floppy drive system. It was also sold in an optional 4' high 19" rack mount cabinet with wheels, version C3-B, that included a hard drive. This was intended for an office environment and used a standard computer terminal, like the Hazeltine 1420 (or 1500), which was optionally supplied through factory sales. The terminals were the same ones as used with mainframe computers of that era. With the largest hard drive available, 74MB, the system cost just under $13,000. The least expensive version without the rack or hard drive was $3995 MSRP, a phenomenal performance-to-cost ratio for the time. The Challenger III also had the capability to support non-floppy or hard drive Challenger 2P computers through a simple network using RS-232 links.

OSI's later products were also 6502-based, the Superboard II, Challenger 1P, Challenger 2P, Challenger 4P and Challenger 8P, introduced in 1979 and discontinued in 1981.

Original Ohio Scientific motherboard designs used 7400-series TTL chips. Instead of using a floppy disk controller IC, OSI used a Motorola MC6850 ACIA Serial Port ACIA chip and a Motorola MC6821 (PIA) chip for the Disk Drive Controller, which made OSI 8" & 5-1/4" Floppy Disks unreadable by other computer systems.

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