16 Feb
2014
16 Feb
'14
12:50 p.m.
Just curious as to what the expert opinion is on this - I've got a
ST412-type drive here (it's a Miniscribe with 615/4/17 ~20MB geometry)
which refuses to read from cylinders 128-255 or cylinders 384-511 - giving
address mark not found errors - although cylinders outside those two ranges
are fine.
The way the faults lie exactly within a couple of specific bit patterns
(01xxxxxxx and 11xxxxxxx) for the cylinder number makes it seem more like a
controller problem to me - but I don't know how much logic there is on a
ST412-type drive, what with the buffered seek ability.
My first guessis that for some reason the controller is losing the 128's
bit from the cylidner register and is, in fact, goign to the wrong cylinder.
A couple of ideas :
Is there a command that will read the sector headers fro mthe currnet
cylinder? If so, seek to cylinder 128, say, and red the headers to see
wht cylinder iut is acutally on.
Seocndly, is any part of the positioner mechanism visible outside the HDA
(some drives had a 'flag' and optoswitch on the stepper spindle for the
track 0 posiiton sensor, this 'flag' moves as the heads seek. If so, then
seek to cylinder 127, then seek to cylinder 128. If the positioner moves
a fair distance -- and in the wrong driection -- you will know something
is up.
This sounds much more like a controller than a drive problem to me.
-tony