RL02K Pack Reliability/Characteristics

[Christopher Parish]

Thanks for your help everyone.  I finally figured out what was happening.  Something is wrong with my (everyone's?) drives.  Every once in a while I get stuck on a track.  The drive has no conception of where it is cylinder-wise.  It just accepts a difference in track number and direction, so something like this was occurring:

Current Track:0  Desired track:1  Commanded Difference:+1
Current Track:0  Desired track:1  Commanded Difference:+1
... Repeat N times ...
Current Track:0  Desired track:1  Commanded Difference:+1

I've fixed it by having my controller perturb the track number after several (5) unsuccessful seeks:

Current Track:0  Desired track:1  Commanded Difference:+1
...
Current Track:0  Desired track:1  Commanded Difference:+1
Current Track:0  Desired track:1  Commanded Difference:+2
Current Track:2  Desired track:1  Commanded Difference:-1
Current Track:1  Desired track:1  Commanded Difference:0 (YAY!)

In the process, I have confirmed that sometimes the drive does mis-seek when making larger jumps across the pack.  A single follow up seek is almost always enough.

I have a feeling this is related to the the special things the RL02 does when making single track movements (kick pulses?) that must not be working very well in my drives.  Of course, this could be totally normal, and the controllers/software drivers hide it.  Regardless, it never hurts to make the controller more robust than it needs to be.

Christopher