• Please review our updated Terms and Rules here

Found an Ohio Scientific Challenger III Today

glitch

glitch

Veteran Member
Joined
Feb 1, 2010
Messages
5,051
Location
Central VA
It's finally staying warm enough here to work in the warehouse attached to the building I work in, so I thought it might be a good day to inventory more of the stuff on the shelves. As luck would have it, there wasn't going to be any real work happening, because under a stack of very large cardboard boxes sat an OSI Challenger III!

The Challenger III was a late-70's system with one really strange feature: it had three processors on the system board: a 6502, 6800 and Z-80. This one has all three installed, and is still jumpered for 6502 on boot-up. It also had 3x 16K static RAM boards, a floppy board, and two others I haven't identified yet. There are also two Panasonic single-sided 8" floppy drives in the cabinet.

I didn't have a lot of time to play with it before heading home, but I pulled all of the boards and drive power supplies, and brought it up on a variac. All of the supplies came up and regulated just fine (+5, +12, +24 and -9). I plugged in the processor board (which also contains ROM and a 6850 for console) and a 16K RAM board, but couldn't get the system to sign on. The cabinet is pretty dirty, but the boards are intact, so it looks like that will be another project after I get the Z-2D up and running.

While this OSI didn't come with manuals, I do have access to the complete system software library, manuals, schematics, et c., because my boss's first business computer was a DIY Challenger III, complete with 29 MB 14" Shugart hard drive. He's currently working with me to get it up and running as well, since he's got a lot of software he wrote that he'd like to get back. Of special note is a hand-written word processor for OS-65U. More information to come!
 
I believe the one my boss has is a C3 (separate floppy and hard disk cabinets) while the one I found is a C3P (floppy + system in the same cabinet). I'm not sure if that assessment is correct -- feel free to enlighten me!
 
Yes, pictures coming soon! I forgot to take my camera today, or I'd have taken some.

I did manage to get the system to sign on partly today! After reconfiguring one of the 16 K static RAM boards for 0x0000 partition 0 (the OSI bank switching scheme) and verifying the processor board was actually set to 9600 baud, I got the "H/D/M?" prompt on reset! Trouble is, nothing happens once you press a key for selection...even if it's an invalid key. At least this shows the 6502 is alive and can read from ROM, as well as writing to the ACIA. I don't know if the monitor is accessing RAM by that point, but I presume it does as nothing worked before I fixed the strapping on the RAM board.

I also gave one of the 8" floppy drives some love today. The spindle motor was mostly seized, and the head assembly was more or less stuck to the stepper screw. A lot of lithium grease later, and it runs smoothly. When used with my boss's CPU board, which doesn't have a monitor ROM and tries to boot directly to floppy, the head loads and the stepper jumps around a little. I don't think it's meaningful as it doesn't seek Track 0 when it starts.

We pulled out the 8" disks for my boss's system today...he's got all of the original disks, plus original Forth masters, as well as CP/M and the OSI CP/M "Escort Disk" (this was required since the Challenger III boots with the 6502 enabled). We've also got all of the original manuals, which I've been reading through as time permits.
 
It Lives!

It Lives!

In reading through the OSI manuals, I discovered a handwritten note concerning the ROM monitor -- "Caps lock **MUST** be on!!!" Turns out the H/D/M? is case-sensitive. Pressing M drops you to monitor, though the system doesn't make an effort to let you know (it just does a CR-LF, no prompt or anything). Pressing D caused a head load, but no stepper activity. I manually advanced the stepper to something past Track 0, and still nothing.

I think the drive I was using has a stuck Track 0 sensor...probably always returning true. After reconfiguring the jumpers on a Shugart SA-800, I did manage to get the system to boot into OS-65D. I dropped from the BASIC system into kernel mode and formatted a disk just fine, though with a single drive I can't copy from disk to disk. So I'll probably work on that Track 0 sensor tonight and get that taken care of!

I brought the system home from work, since the SA-800 was at home, so there will be pictures shortly! The OSI 510 CPU board is an earlier revision than has been documented elsewhere on the Internet, so I'll be taking pictures of that and dumping the ROMs for preservation. Fortunately, I've got a PROM programmer that will handle 1702s!
 
Very cool. Did you... say 14" hard drive up there? I need a 14" hard drive. It would sound and look beautiful.
 
You must log in or register to reply here.
Back
Top