[Coco] Re: Drive speed incompatibilities

[Gene Heskett]

On Thursday 13 November 2003 07:51, fsteeman at dds.nl wrote:
>OK, thanks for that program RPM.BAS ! It was just what I was looking
> for and it works perfectly! OK, I have now determined that my new
> drive 0 is slightly off in speed from my old drive. In fact, my old
> drive 0 turns at almost 303 rpm whereas my new drive 0 has a speed
> of about 299. It is not much and just in between the 1.5% margin,
> but it would certainly explain why my new drive cannot read my old
> floppies.
>
>The question now is: OK now I know that the drive speeds are
> different, what do I do next? Is it at all possible to adjust the
> drive speeds?
>
>Cheers,
>
>Fedor

Sometimes bit its often very drive specific.  Follow the wires from 
the spindle motor to the board andsee if the is an adjustment in the 
area of that circuitry.

Now, the fast drive.  That can be a problem because it would use up 
the normally unused sync data between the end of the last sector of 
the track, and the index pulse which marks the beginning of the 
track.  If this shorrt area gets toos hort, the last sector can 
actually overwrite the beginning of the first sector.  At that point 
of course, even the formatting is trashed and I think it will tell 
you so during the verify phase.

Slow drives on the other hand, normally go undetected by any means 
until you hit a newer drive and the data recovery pll cannot follow 
the increase in the data rate the new drive sees.  I've never 
actually seen that happen though, and I'd suspect that far more of 
your interchange troubles are created by slightly out of tolerance 
track zero locations.  That and the possibility the old drive is a 
40tpi, and the newer drive has 80tpi width heads.

>
>PS: Not to criticize, but just one line that ought to be added to
> the RPM.BAS program would be: 5 WIDTH 80

-- 
Cheers, Gene
AMD K6-III at 500mhz 320M
Athlon1600XP at 1400mhz  512M
99.27% setiathome rank, not too shabby for a WV hillbilly
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Copyright 2003 by Maurice Eugene Heskett, all rights reserved.