[Coco] 3.5 drives was drive motors

[Phill Harvey-Smith]

On 13/07/2013 16:49, Bill Pierce wrote:
>
> Also, if you're using an 3.5 HD drive (1.44 meg). It must be jumpered
> to work as 720k or it will not work. If there's no jumpers, then it's
> the wrong type drive.

I have *NEVER* knowingly seen a 3.5" 1.44MB drive with a jumper to 
select 720K mode, and I've seen a fair few in my time :) :)

I have seen such a thing on a 5.25" 1.2MB drive but on these the spindle 
rate is different for HD and DD disks, this is not the case with PC 
1.44MB drives.

>		It seems I remember that some drives would go
> into 720k mode if you cover the hole on the upper left of the disk,

Or better still use proper 720K media, most drives will auto switch data 
rates / head write current when the correct disk is used. I have a pair 
of Sony 1.44MB drives that I have used successfully on a multitude of 
retro systems as 720K disks without problems using the correct media.

> but I think that's only on a PC. The HD disks will work on a 720k
> drive but will possibly fail eventually. Something about the 720k
> write heads not being strong enough for the HD media. Anyway, it's
> best to have 720k disks (DD).

That is correct, or so I am lead to believe, though in the couple of 
experiments I have conducted they worked but I didn't test long term.

The other things is that a PC 1.44MB drive will work unmodified in a 
CoCo as drive 1 (second drive), if you want it to work as drive 0, you 
will need a cable that swaps pins 10 and 12, note this is not the same 
as a PC cable :)

Cheers.

Phill.


-- 
Phill Harvey-Smith, Programmer, Hardware hacker, and general eccentric !

"You can twist perceptions, but reality won't budge" -- Rush.