IBM DDRS-39130 - Ultrastar 9.1 GB Hard Drive Specifications page 105

When there is a command active or in the queue, the LED is high.
Command Aging Limit This value is used to control the maximum time a command should wait in the
command queue when the CAEN bit is set. Each unit of this timer is 50ms.
QPE Read Threshold specifies the error reporting threshold for read operations when the QPE bit is set
to one.
QPE Write Threshold specifies the error reporting threshold for write operations when the QPE bit is set
to one.
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SCSI C O M M A N D SET