There’s more than you’d think
When it comes to DOS (disk operating system), most older hands are familiar with MS-DOS, or Microsoft Disk operating system. Most computers, including the coco had versions of MS-dos, using similar commands. while i cannot speak for all retro computers, the coco had a couple more dos choices.
while rs-dos was certainly popular, being the dos of choice for almost everyone with a radio shack disk controller (yes, an eeprom could be subbed in with ados or jdos or something else), there were a few other controller designs as well. disto products and j&M systems both created very capable disk drive controllers with advanced dos versions as well.
this isn’t going to be an exhaustive post – i simply don’t have the experience with the different versions. although i did use A-dos a few years back in one of my fd-501 controllers, my memory of it has faded. the reason for the post, though is two-fold, both reason involve timing. recently I picked up a J&M controller board from eBay.
This one does work, and has an RS-DOS ROM in it. What it lacked was a case. One of my other, lessser known hobbies, is 3D printing. So after some quality time with some dial calipers, and the requisite three design revisions, I printed a PLA FDC case for my J&M controller:
As i said earlier, I’m not able to do a comprehensive analysis of the different DOS’s. For example, JDOS and ADOS both have many additions in functionality and commands. JDOS appears to have versions compatible with the CoCo 1, 2 & 3; while ADOS appears to be CoCo3 specific, though don’t hold me to that. in a subsequent post, I’ll add pics of my next J&M controller – which has selectable DOS and a parallel port.
if you’re interested in more info on Jdos, check out the documentation for it at the Color Computer Archive; and you can check out ADOS and others while there.
Additionally, Ken over at Conadian Retro Things on YouTube recently posted two videos regarding JDOS – once is a run down of some of the commands and differences. The other is showing how the Dysan calibration disks (a ver yrare and disappearing breed) work. Those are linked below.
The following is the rare calibration disk – you may never see another one in the wild again…