[Coco] Re: [Color Computer] 1.44 disk

Wed Aug 3 08:02:56 EDT 2005

On Wednesday 03 August 2005 07:40, Davey Brain wrote:
>Gene Heskett wrote:
>> On Tuesday 02 August 2005 15:38, stacey wrote:
>>>can u use 1.44 diskettes in a 720k drive   will they work ok
>>
>> Generally speaking, no.  The media for the HD disks has a magnetic
>> coating thats harder magneticly, and requires more drive to make
>> an adequate recording.  It might work 5 minutes after you do it,
>> but 2 weeks later all bets are off.
>>
>> I've noticed that todays crop of aftermarket 3.5" floppies also
>> seem to have another problem.  Insert an HD diskette, and they
>> demand a 500 kilobaud data rate and will not function at all at
>> the 250 kilobaud rate the coco controllers can muster.  Same drive
>> with a DD diskette in it works flawlessly at the coco's 250
>> kilobaud data rate.
>
>Hi,
>I held off on this discussion but now I must jump in as we have been
>round & round this topic in the TI-99 groups and I can state with
> 100% confidence that there is absolutely no (zero, nada, zip)
> difference in the magnetic coercivity between 720k and 1.44m
> brand-name floppies; the only major difference is the number of
> holes in the plastic. On the TI-99 they can be used interchangably
> with 100% confidence & reliability.

Maybe the TI99's disk driver hardware runs at 500 kilobaud?  This is 
also the first time anyone has stated that the media is EXACTLY the 
same.  My figures from some time back held that HD media was about 
50% harder in coercivity.  In 5.25" floppies, the difference in the 
surface is quite visible, and in the cases where I've slide the door 
back to look at the 3.5's, the HD's always had the smoother, darker 
coating.

Here, I've tried it with the hd hole both open, and taped over with 
black tape in case it was a photocell detector, as better drives are.

Neither will allow an HD diskette to function as a DD diskette in any 
of the drives I have, when the controller is running at 250 kilobaud.

> It is only the 5.25" disks 
> where it makes a difference; the magnetic coercivity is different
> between DD (hub ring) & HD (no hub ring). Also, all 3.5" drives
> spin at the same speed whereas 5.25" DD drives spin at 300 rpm and
> HD drives spin at 360 rpm. In another (older) life I was an
> electronics technician with a repair shop and still have much info
> on electronic and computer hardware. So if you desire I can try to
> find my huge hardware/upgrade guides and quote the exact passages
> from those book as I have on the other groups.
>
>If I understand you there are problems between the 720/1.44
> drives/disks on the CoCo. This is most likely from some other cause
> (such as the difference in Kbaud rate as you suggested). On my
> TI-99/4a system (1.44m drive reading/writing 360k) and my Atari
> MegaST2 system (720k drive) I commonly have used both types of
> disks to carry files between it and my main PC with no problems,
> even 2 years later. But I MUST use 360k 5.25" drives/floppies on my
> TI-99 system as 1.2M simply don't work (side note: the uncommon QD
> 720k 5.25" drives DO work at 360k but only with DD/QD floppy disks
> just as on the 360k drives).
>
>As usual YMMV and always back-up important files in more than one
> place.
>
>WarpDavey

-- 
Cheers, Gene
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
99.35% setiathome rank, not too shabby for a WV hillbilly
Yahoo.com and AOL/TW attorneys please note, additions to the above
message by Gene Heskett are:
Copyright 2005 by Maurice Eugene Heskett, all rights reserved.

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