🚀 go-pugleaf

In <47tbk2$ktb@decaxp.harvard.edu>, bb@wjh.harvard.edu (Brent Byer) writes:
>  and since there are 4 data surfaces, a sustained
>  transfer loses one disk revolution after every four revs, for
>  the seek to the next cylinder.  Hence, 4.14 * 4 / 5 = 3.2 .

You don't necessarily loose a whole disk revolution while doing the seek.
The first byte of all the tracks on all the disks DON'T line up.  They are
offset so that if a seek is done at the end of the last track on the cylinder
then just as the seek completes and the servo settles down, the first bytes
of the first track on the next cylinder are coming under the heads.  Also,
it takes a little time (called head settle time) to switch from on track to another
on the same cylinder.  To allow for this, there's a much smaller offset from
on track to another on the same cylinder.

There is little need to read whatever happens to come under the heads
because of this.  The case where reading whatever happens to come under
the heads might be useful would be after a system initiated seek.


Chuck Tribolet
San Jose, CA
 
Silicon Valley - best day job in the world