tagged queueing

1 definition found

tagged queueing - Free On-line Dictionary of Computing (26 May 2007) :

  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)