Ohio Scientific C2-OEM

Ohio Scientific | 1981 | 6502 @ 4MHz | 48KB RAM | No Video | 2x RS232 ports (505 set to 9600baud, 550 set to ??baud)

I've had this love for late '70s and early '80s home computers for a long while, the Apple II+ was my first system after all, and Ohio Scientific is a brand in that era that I find so neat. Their Superboard-series systems are some of the coolest things ever to me, long single-board kit home systems that I think look beautiful, and I love how all the boards are well-spaced with the intent of end-user modification and hacking.

When I was at the October '23 VCF Swap Meet, I saw this C2-OEM sitting at a table. It was $500 with a tote full of software on 8" floppies and said to work with just a few tiny issues, a deal that I thought sounded amazing against what I usually see on eBay (People want over $500 for a completely untested Model 600!) but I wanted to walk the event a few more times and see if anything else came up. Nothing did, the OSI was still there towards the end of the day, so I couldn't pass it up. One PayPal transaction later and it was mine!

Front Back Serial Plate Backplane

As you can see from the outside and backplane shot, we've got a dual-8" (Shugart SA800) monster of a metal chassis with two serial ports, a power cable hanging out the back, a beefy on/off switch, and a nice brown color. It looks its age, nobody's mistaking this for a modern system, and I think that's beautiful. If I have the date format right, I think that serial plate is saying that the system was from 1981 but I may be entirely wrong? I need to look through the disks and manuals I got else maybe there's some sticker somewhere in there with a build date, I'm not sure.

470 505 535 550

Boards-wise we have a 470 with the PIA set up to handle a printer, the 505 CPU + Serial + Floppy Interface (with the A12 Disk Interface board off the back), a 535 48KB DRAM board, and a 550 serial card with one of the up to 16 6850s populated. What that translates to is a 6502 @ 4MHz, 48KB of RAM, two serial ports, a parallel port, and two floppy drives. Pretty nice for being a C2 where half the backplane doesn't get power or so I'd say!

I was able to get a D/W/M? prompt upon plugging this into a serial port but the belt for the top SA800 fell off, the bottom one doesn't seem to load disks as I assume second drive needs to be prompted or it's because one of the head sensors has a weak output which I was informed is basically the one issue with the system, and I couldn't get that 0000 00# prompt that usually hits when you tell it to drop to the monitor. It may just be the RS232 adapter I was using upon initial testing, a cheap USB-RS232 via PL2303 chipset dongle, or so I think? Once I get this hooked up to my modern PC with a nicer quad serial card inside it I'll see if I can get any farther else I guess we'll need to do some troubleshooting!

The plan, as this does have the smaller +5V supply (I think only like 6A?) and I haven't tested that maybe I'm being hit by dead 4116s, is to maybe shoot for one of The Glitch Work's GW-OSI-RAM1 boards which would use less power for more memory. If I can get this running OS65 (of which I have a ton of disks) I'll then hook the SA800s to my Greaseweazle, dump all the floppies I got, upload all that to archive, then either decide if I'm going for a multi-user serial system or if I want to get a video card inside the idiot.

At some point I should probably also consider stripping the rust and paint off the top cover and re-browning it alongside a whole set of screws for holding boards in place. There's a decent amount and it's not eating the system up but hey, if I can give it a fresh coat and protect it for another like 40 years then why not?

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