A disk drive including a disk, a signal measurement circuit to measure
amplitudes of signals received from the host, and a processor for
controlling operations in the disk drive. The processor under the control
of a program in conjunction with the signal measurement circuit: measures
an amplitude of a signal from a host during a first speed negotiation
process and determines if the amplitude of the signal from the host is
above a pre-determined amplitude for the disk drive. If so, the processor
commands the disk drive to transmit the signals to the host at the
measured amplitude of the first speed negotiation process. However, if
the amplitude is below the pre-determined amplitude for the disk drive, a
second speed negotiation process is forced using a low frequency signal
from the host and calculations are performed to determine appropriate
transmit amplitudes for the interconnect.