31 Mar
2015
31 Mar
'15
11:27 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