The Ohio Scientific C4P Page
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C4P system The OSI C4P Page C4P with floppy disk drive


Welcome to the Ohio Scientific C4P page! The OSI C4P was the first real computer I owned. Let me digress. The first computer I ever touched was a Commodore PET; the one with the calculator keys and built-in cassette tape drive. I saw it at a Bay or Eatons in the mall. I was fascinated I started going to the local college's computer lab in the evenings to play with them. Eventually my high-school got some 4032 PETS to replace the old Wang machines we shared with another school. Anyway, I was hooked and couldn't get enough. I wanted my own computer and I started reading magazines and doing research to spend my hard-earned money on the "best" computer. At the time there was not a lot of choice; Commodore PET (no sign of the C64 just yet), Apple II, Atari 400/800, and Radio-Shack TRS-80. After comparing specs of all the machines I chose the OSI C4P because:

I purchased it in July 1981 (see invoice) and immediately started learning everything I could about the machine. I converted some PET BASIC programs, learned 6502 machine language. Eventually I upgraded the machine to 2MHz, added more memory and a floppy drive. I decided I wanted the computer and drive to be in one unit with a detachable keyboard so I started work on building a new case for it. I never completed it.

Of course as with all things computer related, bigger and better was just around the corner, but the OSI C4P was the machine that started it all for me. It is for that reason, and to preserve some of the glory days of the start of the computer revolution that I have created this page.

Eventually the OSI was packed away but not forgotten. Luckily I am a bit of a pack-rat and saved just about everything I had for the OSI. It is now 2006 and in the process of cleaning up my basement I have come across the stuff again. I have taken everything back out and am having fond memories of those days long ago. I found that I might have some stuff of interest so I am trying to document everything. I don't know how much I can do, so if you see anything here that interests you please drop me a line.

Technical Specifications

CPU: 6502 @ 1MHz, overclocked to 2MHz with simple jumper
RAM: 8K expanded to 24K with D&N board
ROM: OSI Monitor, Microsoft Basic
VIDEO: Text 64x32 or 32x32 in 8 colours (or mono).
GRAPHICS: None (use character set). Optional third-party hires board
SOUND: Simple 1-channel Tone Generator, companding DAC (uses CPU to generate waveform).
STORAGE: Cassette, expandable to Floppy Disk
KEYBOARD: Basic 53-key keyboard
IO: Joystick, Serial, Modem, IO ports
EXPANSION: 4-slot backplane (2 used in base system)
CASE: One-piece metal case with integrated keyboard and power supply. Wood-panelled sides.

My System

I have the OSI C4P with D&N floppy drive. I took the computer and drive out of their cases and planned to make a new all-in-one unit out of plexiglass. The top is missing and i never finished it.

The unit powers up but seems to have some problems with the video output. I tried connecting the system to my LCD TV but the display is very dim. It does give me the H/D/M? prompt and I can load OS65D3.3 and some of my other disks but things are hard to read. Because of this I haven't tested all my software yet. I will have to dig out a monochrome monitor to see if that works better.

My C4P system in 1981 My C4P system in 1982 My C4P system in 2006 My C4P system in action

The first two pictures were taken in 1981 and 82. They show my setup back then. The first one when I was using a cassette tape and monitor in case. The second after I upgraded to floppy drive and removed the guts of the monitor from the big bulky case so my system would take less space. By this time I also had my first Commodore 64 computer with cassette tape. The third picture is how my system looks today. I am planning to either build a new case with styling that matches the original machine or restore everything to original condition. The last picture is the machine running OSI Invaders on my 32inch LCD TV.

My OSI stuff doug out from basement in 2006

This is all the stuff I found in the basement. I have some manuals and binders containing schematics, docs, magazine clippings, and OSI-related newsletters.

Superboard II

In 2006, after pulling my C4P system out of storage and getting nostalgic, I came across a guy selling his OSI system on a buy-and-sell site. It turned out he had a Superboard II (600 board) in a custom case, so I purchased it from him (along with a trunkload of Commodore 64 stuff as a bonus). It also came with some books, manuals, and newsletters. The 600 board is mounted in a metal case with wood sides all covered with fake wood-grain mactac. The top comes off for servicing. There are two toggle switches for tape operation.

Superboard II, purchased 2006 Superboard II with top open

Unfortunately the machine is not functional. When I get some time I will attempt to fix it.

Additional C4P

In 2009 I picked up another C4P. This unit is the basic cassette model with an additional RAM board. The RAM board ia a clone of the OSI 527 24K board. Unortunately this unit is also non-functional. I have determined that the 502 CPU board is not working correctly and hopefully it can be fixed. I will update this page if I make any progress.

I purchased this unit to try to restore my system to original condition.

Magazines / Advertisements / Articles

Micro Magazine Popular Electronics Popular Electronics Ad RadioElectronics Buyers Guide RadioElectronics AD July,80

Add On Boards

This is the TOSIE Hacker board. It added a new sound chip, extra ram and new character generator options. Attached to the bottom of the board is (I think) a Mittendorf high-res graphics board.

Front of Hacker board Back of Hacker board Chip layout of Hacker board Hacker PCB board traces (front and back combined)


First book of OSI Third book of OSI Fifth book of OSI


For a complete list of my documentation click HERE. If you are interested in more info on these please contact me. I will try to post rare, unusual, or requested documents here as time permits.


I hope to eventually add some of the software here; some of my PET conversions, or self-made programs.

Links to other OSI resources

Last updated: Oct 21/2010, 4:30pm EST

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