HP SureStore Optical Jukebox 160ex Service Manual page 201

Theory of Operation
Interposer PCA
computer, is buffered on the interposer PCA, and sent to each drive
individually. Req signals come from the drives and are buffered into one
signal going back to the host computer. If a drive problem occurs, there is
a possibility that this problem could be from the interposer's buffering of
the Req and Ack signals. But if the problem is due to Req and Ack, it will
probably affect only one drive.
Chapter 6 6-9