[Coco] Maximum CoCo Drives

Francis Swygert farna at att.net
Thu Jan 23 06:51:51 EST 2020

There are only four drive select lines on a CoCo disk controller, 0-3. The CoCo was set up to from Tandy to handle four physical single sided drives, 35 track. To use double sided drives you lost one of the lines, as it was used as the side select on IBM computer drives (double sided), so only three double sided drives could be used. To go out to 40 tracks (or more) required a DECB modification. ADOS allowed both double sided and 40 track. While DECB couldn't use more than 40 tracks, 80 track drives could be used with OS-9 and the correct drivers. 

I had my custom cased CoCo with two double sided 40 track 5.25" floppies and one 80 track (720K) 3.5" floppy. And a small SCSI hard drive for OS-9. Never really used the HD or 80 track much (never used OS-9 much!). I used a Disto Super Controller with a 4-in-1 board. IIRC I got the board on sale from Tony at one of the Chicago CoCoFests, the parallel port hardware was bad on it, something I didn't intend to use (I only used the SCSI port, IIRC). It was in a Tandy 2000 case with the 3.5" drive mounted in the very center of the front, had to cut a hole in the case for it. When I stopped using the CoCo much I sold it, around 96 or 97. Figured someone who still used it a lot would get more from it than me sticking it in a closet. Wonder what happened to it? I also had a portable mounted in an old Kaypro case with an amber composite monitor I swapped in for the old IBM style monitor. No HD, but I think I had a 3.5" drive in it along with a pair of DS 5.25"... can't recall for sure if it had the 3.5" though. I know I didn't have a HD, had to use a shorty floppy controller. Wonder what happened to those? Unique enough that if someone on here were using them they would know...

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