8-bit Multiuser (was Multics)

Gimix built 6809 (and I believe, later, 68000)-based computers that ran OS-9. Their machines were very well-designed and built, and had a reputation for being true "data center quality" rather than hobbyist machines, though they did market to the "high end" of the hobbyist market. OS-9 was a full multi-user operating system that ran on the 6809 (a 68K-based version which was dramatically enhanced over the 8-bit OS-9 was also marketed, which was quite powerful). The 6809-based (8-bit) version of OS-9 could be run on the various models of the Radio Shack Color Computer, but with floppy disc's I/O bandwidth limitations, it was frustratingly slow on the Coco I. The later Coco II and Coco III made improvements in the I/O architecture, and added some "memory management" capabilities to address some of these problems, and with a hard disk connected, could serve up a small office multi-user environment, although they were hardly what I'd call "data center" grade equipment. OS-9 was made by a company called Microware, and was really quite amazing for its time. Sometime in the 1980's (can't remember exactly when, but I think it was after 1985) I built a homebrew 6809-based computer that used OS-9, and could nicely service five users including the console, all running simultaneously (terminals at 9600 baud), along with background jobs that did things like printer spooling, a clone of UUCP, and even a batch processing system. The system had a DMA/Interrupt-based hard disk controller that I designed that interfaced to a Micropolis 8" hard disk drive (can't remember the model number, but I think it held something like 20MB, and used a pre-SCSI parallel interface, that I got from the Tektronix company store for something like $25), and an 8-port serial I/O card that had some local intelligence (another 6809) that handled buffered input. OS-9 had a very extensible and well-documented driver architecture that made it possible to easily write device drivers for all of this custom hardware. It utilized bank-switched memory (It had 256K of memory in four banks with a common area (I think it was the upper 1K of the 64KB address space) that wasn't bank switched for I/O (the 6809 uses a memory-mapped I/O methodology) and boot ROM. It was a fun project (that was when I had time...don't know where it went, but it's definitely not here now), and I learned a lot by tinkering with it. I still have most of the pieces of that system, except the hard disk eventually died, which pretty much ended the playing with it -- those old Micropolis 8" drives just aren't around anymore, and there's no time to try to design a USB or SCSI interface for it. Those were the days... Rick Bensene The Old Calculator Museum http://oldcalculatormuseum.com