19 Oct
1999
19 Oct
'99
5:56 p.m.
On Tue, 19 Oct 1999, Fred Cisin (XenoSoft) wrote:
On Tue, 19 Oct 1999, Don Maslin wrote:
Nah! Really?
- don
But let's muddy the conversational waters a
bit :) I have no quarrel
with describing a 360k DOS disk as 40 cylinders, but let's consider a
disk such as the Xerox 820-II 5.25" DSDD. Unlike the DOS disk, the
Xerox does not read side 0 first and then continue on to side 1.
Instead, it reads track 0 side 0 and then goes on to read track 1
side 0. Is not it reasonable - perhaps more reasonable - to call the
Xerox disk an 80 track disk? Or better, an 80 track 48 tpi disk.
In addition to disk formats that use all of the sectors of one track, and
then use all of the sectors of the same cylinder's track on the other
side, and then advance to the next cylinder:
Some formats (particularly ones that were once single sided, and then
expanded into DS formats) use all of one side and then use all of the
second side starting over at cylinder 0 of the second side.
Some start over at a later cylinder of the second side (so that the same
number of tracks are "Reserved/skipped" on both sides).
Some use all of the first side and then use the second side counting DOWN.
Thus, after Side 0 Cylinder 38, then side 0 cylinde 39, then Side 1
cylinder 39, then side 1 cylinder 38, . . .
That eliminates having to do a seek back to track^H^H^H^H^H cylinder 0.
Some that use various logical sector skewing will treat the entire
cylinder as a track, thus using one or more sectors from one side followed
by one or more sectors from the other side, back and forth.
And then, there are some that are WEIRD. --
Grumpy Ol' Fred cisin(a)xenosoft.com