This computer was an enhanced version of the Challenger IIp. The motherboard was equipped with 3 microprocessors: 6800, 6502A and Z80. An optional 74 MB harddisk was available ($6000 !).
It was supplied with a word processor called WP-1 and a database called DMS. An enhanced version of the operating system allowed to connect up to 16 terminals to the computer at one time.
About OSI, Frank Leonhardt* adds:
Unfortunately OSI did not get its model numbers straight - it was a very disorganised company. A lot of users got the circuit diagrams for bits of OSI equipment and modified one board to another, as they were all made up of the same parts - and dealers would mix and match boards to build a machine to customers requirements.
Their final machine was the Challenger 5, which was a bit like the Challenger 3 but it had five processors - again, OSI could not decide which 16-bit processor was going to WIN so they added a 68000 and a Z8000 to the C3. They never believed that the 8086 would become popular. I know someone connected to their main dealer who saw something about this, but I don't think they were ever sold.
The 74Mb Winchester disk was real - amazing for 1978. Apparently it was very unreliable until the guy who owned it (Dave Graham) covered the outside of the box with lots and lots of fans.
* Frank was the first Technical Editor for the famous Personal Computer World magazine, England's (Europe's) biggest computer magazine - founded in 1978.
The company I work for owned to C3B computers. Each was a 3 user system with 80 Meg hardrives. One system was older and used less reliable boards. The newer had many less problems. Over time the two systems became one 5 user unit with 2 80 Meg hard drives. We ran that computer non stop 24 7 for serveral years after the OSI company was gone. All the boards had tin plate sockets and were fine as long as the unit remained running. If you had to power down for some reason, you had to open the unit up and remove all the chips from their boards. Clean and reseat them. Over the many years that I operated this computer I had changed out most of the sockets and connectors on the back plane with gold plated parts. When the computer was finally shut off for the last time it was a very reliable unit. Kind of sad tosee it gone. I wish I could find one.