[Coco] Read Coco floppies in my PC

[Frank Swygert]

Bill got a little Celeron 366 MHz HP Pavillion 4450 from me. The HD I installed (a little 4.3GB) had XP already on it and I got it working fine. He also has a DOS 6.22 floppy which I sent with it just in case. All I did was boot that floppy and make sure it went into the install program, but he should be able to exit that and use format.

Most of what Arron has posted is true with 1.2M drives to some extent. I never had a big problem formatting 360K disks on a 1.2M drive and reading it on MOST CoCo drives, but some didn't like it. Older original CoCo drives gave the most trouble. Newer drives (circa early 90s) generally didn't though there were a few exceptions.

In general, use 360K disks for anything you want to keep. A 1.2M disk will work in a pinch for transferring files, but as little as 12 hours later may not have usable data. This is due to the magnetic coating on the disk.

I could format a 360K disk on a 1.2M drive with no problems, and my CoCo drives (Mitumis IIRC) would read them. You cannot write to that disk with anything other than the size drive it was formatted in though. Another 1.2M drive, yes, but not a 360K, and vice-versa. So format and write on the 1.2M, read on the 360K BUT DO NOT WRITE TO IT. The different width heads are the culprit there. For most people this worked, but as I mentioned, some drives (especially older 360K) are a lot pickier than others, so your results will vary.

Bill, contact California Digital (http://www.cadigital.com/flopdriv.htm). Scroll to the bottom of the page and you will find some 360K and even 180K floppy drives (single sided, like all but the last CoCo drives) for $39 and $9, respectively. There is no on-line ordering. In truth this may be an old site, but they also have a Tano Dragon (CoCo 2 clone, $45) and I know someone who bought one from them just two years ago. At other places the drive average about $75 in tested working condition (guaranteed). They average $70 on e-bay, but you can get untested drives for $25-$50 (working when stored pulls). Finding a PC that old at the Goodwill or Salvation Army... those days are pretty much gone, but I have occasionally seen one at a yard sale or "junk" flea market.

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Date: Sat, 31 Mar 2012 00:31:01 -0400
From: Aaron Wolfe<aawolfe at gmail.com>


http://www.oldskool.org/guides/oldonnew/hardware/1.2mb_to_360k.html
"Everybody knows that trying to write to a 360K disk in a 1.2MB drive
usually works fine for the 1.2 MB drive, but then renders the disk
mostly unusable for the 360K drive. "

http://www.brutman.com/PCjr/diskette_handling.html
"A high density 5.25" drive can read a low density diskette just fine,
even though the drive head is narrow compared to the track.  However,
if you try to write to the diskette, you will write a new track of
data that is much narrower than the existing data.  This will
generally make the diskette unreadable in a double density drive.."

http://www.vintage-computer.com/vcforum/archive/index.php/t-12114.html
"You should ALWAYS format the disk in the 360kB drive. Most of the
time writing data in a 1.2MB drive leaves it unreadable in the 360kB
one"

http://www.retrotechnology.com/herbs_stuff/drive.html#12meg
"..ever since the first high-density 1.2Mb drives and media were
introduced for the IBM PC. People compain they can't read 360K
diskettes formatted or written on a 1.2M drive.."

http://books.google.com/books?id=kG8LcWfruOAC&pg=PT145&lpg=PT145
"..once that diskette has been written or formatted in the 1.2 MB
drive, it will no longer be reliably readable in a 360 KB drive."

http://www.linux-tutorial.info/modules.php?name=MContent&pageid=128
"Problems arise if you use a disk formatted at 360K in a 1.2Mb drive."

etc..

-- 
Frank Swygert
Editor - American Motors Cars Magazine
www.amc-mag.com