[Coco] 720k 3.5" floppies

[Mike Pepe]

Joel Ewy wrote:
> Frank Swygert wrote:
>> I know 720K 3.5" floppy (360K and 720K 5.25" also) are getting hard to
>> find, but they are still available at reasonable prices. California
>> Digital is one dealer I know that has them
>> (http://www.cadigital.com/flopdriv.htm -- scroll down near the bottom
>> of the page). 3.5"/720K are $29 (Sony 11W drives), Mitsubishi 501B
>> 360K drives are $39, and TEC 501 180K drives are only $9. Only DECB
>> users might want the single sided drives though, not much point in
>> using them for OS-9. $40 for a 5.25" 360K drive might sound like a
>> lot, but they aren't made any more! Finding good used ones is tough
>> now too, not even the thrift stores usually have something that old,
>> all computers I've seen there lately have at least 1.2M and 1.44M
>> drives, and are usually Pentium class or better. Most of the 486 and
>> lower machines are in the land fill or kept as collectibles.
>> Interestingly I still see a good many 486 laptops around though.
>>
> Maybe I need to dig into my floppy drive stash and do some testing.  I
> don't have many real 720K drives (1.44M drives work fine in their place
> if you use 720K media -- which is also getting hard to find) but I have
> quite a few 360K and 1.2M 5.25" drives, most of which should still be in
> good working order.
> 
> Could one use a 1.2M drive (with HD media) as a 720K drive on a CoCo?
> 
> 
> JCE

Not unless said 1.2M drive is capable of spinning at 300RPM. The IBM 
standard for 1.2M drive spins the media at 360RPM. This speed difference 
increases the data rate and renders it incompatible with the stock CoCo 
controller.

There are a few 1.2M drives out there that can be jumpered to run at 
300RPM. Using standard low density floppies, you would get a 720k drive 
out of it.

If you want 720k, I'd go with the 1.44MB 3.5" floppy and 720k disk 
option. It's a lot easier to obtian, replace, and deal with- they spin 
at the right rate by design.

-Mike