[Coco] Read Coco floppies in my PC

Sat Mar 31 16:14:52 EDT 2012

Yes, you were lucky :)

You'll notice that most of the documentation of this problem uses
words like "mostly, usually, probably" etc.
This is because there certainly were combinations of factors that
could make things work, or at least work fairly often.

Unfortunately, this was not very common, certainly not something to be
relied on.  I was working at Computerland (IBM service/sales) during
those days.  There were so many cases of people reporting broken fdd
due to this problem that IBM actually had us put big red stop sign
shaped stickers on the 5.25 in drives of new systems, with some text
about the DD/HD problem.

While there is certainly some chance that some 1.2MB fdd might writ
some disks the some Coco can read, it is a shot in the dark.

On Sat, Mar 31, 2012 at 4:40 PM, Frank Pittel <fwp at deepthought.com> wrote:
> Maybe I was just lucky? Then again it's been far to long ago for me to care.
>
> I do remember it was a big issue at the time and the reason I had both sizes
> in my machine. When writing a 360K floppy for someone else i would use the right
> sized drive.
>
> The Other Frank
>
>
> On Sat, Mar 31, 2012 at 12:31:01AM -0400, Aaron Wolfe wrote:
>> 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..
>>
>>
>>
>>
>> On Sat, Mar 31, 2012 at 12:11 AM, Chad H <chadbh74 at hotmail.com> wrote:
>> > Sorry..nothing against you...but I've spent most of my adult life doing things microsoft said couldn't be done.
>> >
>> > I think in all fairness, whether one has problems or not with this 360k issue depends on what combination of OS + Drive model they are using to work with thr 360k media..  I've used win98 almost exclusively with good TEAC and Fujitsu drives
>> >
>> > Aaron Wolfe <aawolfe at gmail.com> wrote:
>> >
>> >>Your results are atypical.
>> >>
>> >>The problems between 1.2mb drives and 360k drives are very well known.
>> >> This used to be common knowledge, but I guess its been a good long
>> >>time since anything regarding floppy disks was well known.
>> >>
>> >>For instance, this microsoft article details the problem:
>> >>
>> >>http://support.microsoft.com/kb/79538
>> >>
>> >>You will find further documentation in the wikipedia article on floppy disks:
>> >>
>> >>http://en.wikipedia.org/wiki/Floppy_disk#5+1.E2.81.844-inch_floppy_disk
>> >>
>> >>The crux of the issue is that 1.2MB FDD use a narrower track than 360k
>> >>disks by design.  The read head on a 1.2MB FDD can easily read the
>> >>wide tracks written by a 360k drive, and it can also read the narrower
>> >>tracks written by 1.2MB drives.  However, 360k drives cannot usually
>> >>read the narrow tracks written by a 1.2MB drive.  This means writing
>> >>to a 360k disk with a 1.2MB drive generally renders the disk
>> >>unreadable by 360k drives.  This is a physical property of the write
>> >>head and not something changeable via software.
>> >>
>> >>
>> >>..
>> >>
>> >>On Fri, Mar 30, 2012 at 11:53 PM, Chad H <chadbh74 at hotmail.com> wrote:
>> >>> I have 9 360k pc-xt drives, all fully tested to read/write disks formatted by 1.2 mb drives without problems....?????
>> >>>
>> >>> Michael Graham <mkgraham at gmx.com> wrote:
>> >>>
>> >>>>Just FYI, most double-density (360k) drives won't read double-density
>> >>>>disks written on high-density (1.2M) drives.  I tried this when I first
>> >>>>got my PCjr, and it didn't work, so I had to swap the 360k drive back
>> >>>>and forth between my PCjr and my old desktop machine until I could
>> >>>>source another 360k drive.  I couldn't get disks written in a 1.2M drive
>> >>>>to read on my CoCo, either.  However, disks written with a 360k drive
>> >>>>will read back just fine on a 1.2M drive, as long as you don't try to
>> >>>>write to them.
>> >>>>
>> >>>>On 3/30/2012 8:20 PM, Bill wrote:
>> >>>>> The drives I just got are 1.2Mb, and I have tried several times to format a
>> >>>>> 360K disk, but for some reason it won't let me. I type in the command format
>> >>>>> b: /f:360 (which SHOULD work), but it gives me an error message.
>> >>>>>
>> >>>>> Has ANYONE been successful formatting a 360K disk in XP with a  1.2Mb drive?
>> >>>>>
>> >>>>> Thanks
>> >>>>>
>> >>>>>
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>> >>>>
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