[Coco] 3.5" FD drives

[Dave Philipsen]

There is a lot of discussion on this if you search the internet.  I have 
personally found that you can write DD disks in a HD drive without 
problems.  Others swear that you'll have a problem.  Since the HD 
floppies generally require a higher recording strength to store data at 
that density it makes sense that perhaps a DD controller may not have 
enough power to overcome a pre-existing HD format.  So it may be better 
to use non-formatted disks that have never been used to record HD.  You 
might also improve your chances by bulk erasing (degaussing) an HD 
diskette before using it as DD.

Read "A note on DD and HD 3.5" disks here: 
http://www.soundtracker.org/raw/cwfloppy/

Another good discussion here: 
http://www.retrotechnology.com/herbs_stuff/guzis.html


Dave



On 7/24/2015 10:19 PM, Al Hartman wrote:
> You are only going to be able to use these on a Coco as a 720k drive 
> with DSDD 720k media. Unless you modify the Controller for HD 
> operation, you won't be able to use them as 1.44mg drives with HD media.
>
> I would not recommend using HD media and taping over the HD sense hole 
> to reduce the writes to DSDD mode, you are asking for data loss over 
> the medium to long term. No matter what anyone tells you, DD and HD 
> media *IS* different, and is meant to take the data at different write 
> densities.
>
> As Mr. Scott was heard to say in one of the Star Trek movies, "Use the 
> right tool for the right job!"
>
> -[ Al ]-
>
>
> -----Original Message----- From: dave
>
> You are correct.  These drives don't even have the solder pads. As far
> as I can tell you'd have to do the select with the cable.
>
> Dave Philipsen
>
>
> On , Bruce W. Calkins wrote:
>> I would expect (and don't mind being proven wrong) that drives of that
>> late a manufacture would have solder pads.  Generally 2 sets 1 of
>> which will have a solder bridge.  To change it over you would remove
>> the solder and bridge the other set.  By that date it was rare to find
>> the full 4 sets of solder pads, jumpers or a 4 position switch. I
>> snagged a few 3.5" drives decades ago that had a 4 position switch,
>> but outside of my collection it has been a very long time since I've
>> seen one.
>>
>> Bruce W.
>>
>>
>>
>> ----- Original Message -----
>>
>> From: "Dave Philipsen"
>>
>>> I'm not sure if they have jumpers.  I'll have to check at the shop 
>>> later today.  Typically, this sort of drive selects by means of the 
>>> ribbon cable.
>>>
>>> On 7/24/2015 8:54 AM, Kip Koon wrote:
>>>> Hi Dave,
>>>> What jumper settings are available?
>>>>
>>>> Kip Koon
>>
>>>>> -----Original Message-----
>>>>> On Behalf Of dave
>>
>>>>>
>>>>> I have 24 new old-stock floppy drives.  They are 3.5" 1.44MB 
>>>>> drives made by NEC.
>>
>>>>>
>>>>> Dave Philipsen
>>
>>
>> ---
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