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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, 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 2P, 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 original Superboard was the least expensive computer with an onboard BASIC programming language of its day commonly retailing in the $300 range. However, it came without a case or power supply. It was a single board computer with the keyboard integral to the printed circuit board. It shipped with 4KB of RAM (upgradable to 8KB), an 4KB operating system in ROM (known as SYNMON as the ROM was labelled 'SYN600') and an early version of Microsoft 8K BASIC.
The version OSI C1P / 600D Superboard II (occasionally advertised as the 'Colorboard') featured an unpopulated socket for an extra 1k × 4-bits of video RAM to hold character colour information. The implementation of this was detailed in the OSI user group newsletter which was published around four times a year. The 600D also featured two video modes: 32×32 (~24×24 visible) for 'graphics', or 64×16 (~48×15 visible) for text where each text line had a blank line between it and the next. The mode could be selected by a poke to the keyboard register. The keyboard polling register (a simple 8-bit TTL Latch) was also used as a very crude digital-to-analogue converter by means of a resistor ladder connected to an 'audio out' socket to the right of the keyboard.
Unusual for the day, but reflecting the home built nature of personal computers of this era, the company supplied full schematics of their hardware. This allowed for third-party companies to create after-market field modifications, such as increased clock speed, increasing the cassette tape drive storage 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. The computer couldn't 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.
Software was also minimal: 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 much handier than reading and writing cassettes at 1200 baud.
Mainly due to the popularity of a UK clone of the Superboard computer called the 'UK-101', the bugs in the BASIC ROMs were eventually fixed, and at least two third-party companies produced their own version of the OS. One version was called 'CEGMON', the other was 'WEMON' produced by Watford Electronics in the UK. Both featured full screen editing (almost identical to the commodore PET), Named cassette file handling (like the PET) and a greatly Improved machine code monitor (also very similar to the Commodore PET).
The OSI Challenger III had three processors: a 6502, a 6800, and a Z80. These were software switchable, but only one would be running at a time. Because it had a Z80, the Challenger III could run CP/M, but it booted up in 6502 mode, and the bootstrap would switch processors.
The operating systems which ran on the CIII were OSI CP/M, OS-65D, and OS-65U. All three OS's, at least in the later versions, had directories with file names.
OSI/CPM had an assembler, FORTRAN and COBOL compiler, but to make a copy of the CP/M, one had to boot in OS-65D to copy the disk. OS-65D had a Basic interpreter, Assembler, Editor, disassembler, and disk copy utility. OS-65U had a Basic interpreter, and had some simple networking capability, but assembly programs had to be done in OS-65D and then ported over.
The company was founded by Mike and Charity Cheiky in 1975 in Hiram, Ohio. Their earliest products were MOS 6502-based systems, the same processor used in the Commodore PET and many other early micros. The company initially sold a computer trainer, which consisted of the 6502 and enough circuitry to communicate with the processor using switches. This was first advertised for $99 in the February 1976 edition of Byte Magazine.
If the trainer was successfully assembled, the owner could trade it, along with another $10, for the company's "OSI 400 Superboard System", a fully developed single-board microcomputer that could run with either the 6502 or the Motorola 6800. The bare boards were available for as little as $29, or in a variety of kit versions with more or less of the parts needed to build it out. It could support up to eight National Semiconductor 2102 SRAM memory chips for 1024 bytes (1 KB) of RAM, 512 bytes of ROM, an ACIA serial interface chip for RS-232C or a 20 mA current loop interface for a teletype, a PIA for 16-parallel I/O lines, and a power supply. Adding a terminal or teletype completed the system. The company also sold one of the earliest floppy disk interfaces and a video card for use with a composite monitor.
By 1978 the company introduced a new main CPU card design, the model 500. This was primarily sold as part of their new Challenger microcomputer systems, but was also available in the Superboard II form. The base model Superboard was essentially the same card as the Challenger, complete with the keyboard, however other versions were available that split out the functionality into separate cards connected together along a 8-connector backplane using 48-pin Molex connectors.
End of OSI
In March 1981 OSI was sold to M/A-Com Inc. of Burlington MA. OSI then concentrated concentrate on business systems. In May 1982 the OSI name was changed to M/A-Com Office Systems Inc.
The Compukit UK101 is virtually a clone of the Ohio Scientific Superboard
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