Re: Apple2 disk controller questions

["Fabrice Frances" <frances@ensica.NOSPAM.fr>]

Supertimer a �crit dans le message
<19990512013929.16539.00000804@ng-fz1.aol.com>...
>Actually, Apple II disks are GCR encoded.  The 5.25" ones
>are single sided, double density.  That's why they store only
>144k, a little less than half of a double sided, double density
>DOS FAT 5.25" disk (320k).

right, 160 or 180 KB for a single sided 5"1/4 DOS disk (resp.
eight and nine 512-bytes sectors per track).

> Apple II double sided, double
>density 3.5" disks are also GCR (800k).  Apple II double
>sided, double density disks are MFM (1.44MB).
>
>GCR is no less efficient than MFM, unlike FM which is less
>efficient.  In fact, Apple II and Macs squish 800k into a disk
>that Win/DOS PCs format to 720k!

there's still something confusing me...
It seems 343 GCR-encoded bytes are transfered through the
disk controller for a single 256-bytes sector... I would say
GCR efficiency lies between FM (512) and MFM (256),
am I wrong ?
Oh, just an idea... I know that Macs use CLV and not CAV
with double density 3"1/2 disks, is it the same for Apple II
5"1/4 drives ?
This would mean more sectors are stored in the outer tracks
than the inner tracks, is it the case ?

Fabrice