20 Jun
2007
20 Jun
'07
4:45 a.m.
On 6/20/07, Jim Leonard <trixter at oldskool.org> wrote:
XDF, IMO, is unnecessarily complicated and not very robust -- they pack
8K clusters on the inner tracks like sardines. But it does indeed store
1.86MB on a DSHD 3.5" disk.
If I were to implement some additional-storage format, I'd probably put
more/larger sectors on the outer tracks where there is more surface
area. I believe Mac and Amiga formats did this, although I'm not aware
of the particulars.
With PC hardware, the sector size is irrelevant with respect to inner versus
outer tracks. 3.5 inch drives have a constant RPM and a constant write clock
rate, so will record the same number of bits on every track. That's where
the unformatted size of a diskette comes from, it's derived from the number
of bytes that will fit in one track without any gaps, headers or address
marks. If you could fiddle the write clock to use the 1 MHz rate for the
outer tracks you might get somewhere. You could work out the bits per lineal
inch at the inner and outer radii, and see if the media will support a
doubled clock rate at the outer tracks.
Regards,
Don Hills