Methods and apparatuses that enable memory devices to inform graphical
processing systems about the results of WRITE de-skew training. A
WRITE-TRAINING mode is added to a memory device. When the WRITE-TRAINING
mode is asserted the memory data mask (DM) pin is converted to an output
port. Incoming WRITE data is strobed-into the memory device and the
resulting data pattern is compared to a desired pattern. If the incoming
WRITE data and strobed-in data match, that result is sent to the
graphical processing system by setting the DM pin HIGH. If the incoming
WRITE data and the strobed-in data do not match, that result is sent to
the graphical processing system by setting the DM pin LOW. Beneficially,
the incoming data and the desired pattern are derived from pseudo random
bit sequence (PRBS) sources.