from
The Free On-line Dictionary of Computing (8 July 2008)
tagged queueing
<hardware> A method allowing a device or {controller} to
process commands received from a {device driver} out of order.
It requires that the device driver attaches a tag to each
command which the controller or device can later use to
identify the response to the command.
Tagged queueing can speed up processing considerably if a
controller serves devices of very different speeds, such as an
{SCSI} controller serving a mix of {CD-ROMs} and high-speed
{disks}. In such cases if a request to fetch data from the
CD-ROM is shortly followed by a request to read from the disk,
the controller doesn't have to wait for the CD-ROM to fetch
the data, it can instead instruct the disk to fetch the data
and return the value to the device driver, while the CD-ROM is
probably still {seeking}.
(1997-07-04)