A computer system includes a first and a second integrated circuit coupled
by a communication link. The communication link operates in a power
savings mode in which data is not transmitted over the link.
Periodically, the communication link enters a training phase in which
training patterns are transmitted over the communication link for a
predetermined time period. The communication link returns to the power
savings mode after the predetermined time period has elapsed. At least
one sideband signal, separate from the communication link, and coupled
between the first and second integrated circuits, is used to indicate
when to enter the training phase from the power savings mode and exit the
training phase and return to the power savings mode.