31 Mar
2015
31 Mar
'15
11:09 p.m.
This sounds strange. Are you sure you are not just
fiddling with the
head here? A head switch will taste like a seek, but it might actually
not move you as you would expect...
Johnny
The head bit is not adjacent to the cylinder offset field in the command word, and
I've verified with the logic analyzer that my intended commands are being sent.
Actually, it's ironic because the head alignment on my drive is near perfect. I can
switch heads and I am on the same track, opposite side, every time.
Now I'm almost certain this seeking problem has something to do with the logic on the
drive because so far, the drive only ever mis-seeks when trying to land on an odd numbered
track. The controller re-issues the seek, but there's a time penalty.
A normal single track seek on my drive takes ~12ms. Most bad seeks to odd numbered tracks
tend to take me an additional track beyond what I wanted, requiring another ~12ms seek to
get back on track. Not that performance is a key factor here, but I'd like to
understand why this is happening.
Christopher