17 Jun
2015
17 Jun
'15
10:59 a.m.
[Writing alignment disks]
It was probably still a voice coil mechanism, but with very differnet drive
electronics.
The RK06/07 do not have embedded servo. There are 2 disks, 4 surfaces in the pack. One is
a dedicated servo surface. That cannot be rewritten in the field, AFAIK the data surfaces
can be
reformatted.
Sure. The low-track-density drives like the RK05 (HP7900, IBM whatever) don't have a
servo
signal on the disk. They have an optical position transducer on the positioner for head
position
feedback. So they can get the heads into position on a totally blank disk. And thus can
reformat
such a disk.
No the procedure I was thinking of was to re-write the dedicated servo surface on the
fixed
disk stack of a fixed/removeable drive that used a servo signal from the disk. I am pretty
sure
it was an HP drive, maybe the 7905 or 7906 (I don't have either).
-tony
I have an idea
that some of these units used an optical interferometer to
determine the head position
Quite possible. But it also requires the movement control being
different from a standard drive, in order to drive at the precision, as
well as the feedback from the inferometer. While the
servo surface can't be re-written in the field (that is what determines
head positions, after all), I see no reason why the data surfaces can't be
reformatted on a drive which has a separate servo surface like the RK06/07
Oh, agree. As long as the servo track is ok, the rest is easy. I was
specifically referring to the servo tracks. (Which on something like the
RL drives is embedded with the data.) Incidentally,
I once saw a procedure (maybe HP) for rewriting the servo surface of
a fixed/removeable drive in the field. It used special electronics, but not any special
mechanics. It went like this :
[...]
Well, a drive like the RK05 can also be reformatted in the field. So it
all depends on the drive...