🚀 go-pugleaf

     
Questions about "THUNK THUNK THUNK" on a flaky hard disk...
The "THUNK" noise was a very rapid head seek, probably to the
beginning or end of travel.  Why?  It could have several causes.
     
Usually, the heads get lost and can't find either the cylinder
marks (loud thunk) or the end-of-travel marks (louder thunk).
     
I think the heads got out of sync with the controller, i.e. heads
on cylinder 200, controller on cylinder 120.  I'm not too familiar
with how the recovery for this is set up, but some drives will do a
Return-To-Zero seek to settle the question.
     
If you have a few things dropping out at once, i.e. a flaky controller
board, then the RTZ sensor might not be picking up and you'll get a
head slam.  These noises are scary, but rather harmless as far as
permanent damage goes on a winchester.  (On the old CDC Hawk drives,
a head slam was sometimes catostrophic.  The Forward-End-Of-Travel
stop would break off and make many itty-bitty marks all over the disk
and anything else it would hit.  But I digress...)
     
Now - for the cause: Your DMA chip may be what's doing it, but don't
bet your life on it.  If the data gets mangled anywhere on its way from
disk to memory, it can give a bad cylinder number (most likely it'll say
it's on cylinder 0 when it's not, but that isn't the only possibility).
Hence, a quick seek to find the proper track again - "THUNK".
     
If the thunk is a head slam, your controller may be what's gone flaky.
Check it over for loose connections, push down on the chips to make
sure they're seated right.  If you are comfortable with socketing chips,
you might reseat them while you're at it.  Look at all the solder
connections real closely - one might not be done right.
     
It's hard to say just what's causing it.  Sorry I can't be more help
than this.  Rest assured, though - your disk probably isn't committing
suicide.
                                                     ---Duck