The SCSI standard supports the notion of ``linked commands.'' Linked
commands allow several commands to be queued consecutively to a single SCSI
device. The 28 variable specifies the number of linked
commands allowed. This variable should be set to 1 if command linking is
not supported. At this time, however, the high-level SCSI code will not
take advantage of this feature.
Linked commands are fundamentally different from multiple outstanding
commands (as described by the 29 variable). Linked commands
always go to the same SCSI target and do not necessarily involve a
RESELECTION phase. Further, linked commands eliminate the ARBITRATION,
SELECTION, and MESSAGE OUT phases on all commands after the first one in
the set. In contrast, multiple outstanding commands may be sent to an
arbitrary SCSI target, and <#1276#> require<#1276#> the ARBITRATION, SELECTION,
MESSAGE OUT, and RESELECTION phases.