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   Message 136 of 190
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   Re: C128D  more options
   
   
   Author:   Nicolas Welte
   Email: welte@chemie.uni-konstanz.de
   Date: 1998/12/30
   Forums: comp.sys.cbm
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Cameron Kaiser wrote:
>
> Nicolas Welte <welte@chemie.uni-konstanz.de> writes:
>
> >bit 76543210   of memory location 106
> >    BHRRRRRR   5,25" drives, B=bump,H=halftrack,R=retries
> >    BXRRRRRR   3,5"  drives, B=bump,X=don't care, R=retries
>
> (It's location 48 in the 1581, but who's counting? :-)

Another reason why to use u0>r rahter than doing a memory write ;-)

> My question is, why no "seeks" in the 1581?

You mean the retries on adjacent halftracks? I think it would be quite
useless, since all of the 80 tracks are used in the 1581. In the 1571,
an 80 track stepper motor with a 40 track R/W head is used. Therefore
only 40 tracks are useable and the other 40 which are inbetween the
actually used ones are called halftracks. If the drive is sitting on
such a halftrack, it might not find valid data, and this is why it has
to retry on adjacent (half)tracks if data is more readable there. If the
1581 steps onto the next physical track, it already arrived on the next
logical track, as well.

Nicolas
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