Patent ID: 6948017

Claim:
A method for communicating among subsystems coupled to a bus of a computer system, the method comprising the steps of: a) operating N subsystems at independent clock frequencies when the subsystems are not communicating with one another on the bus, wherein communication among the subsystems is by a bus-based protocol in which a subsystem granted access to the bus has exclusive use of the bus, wherein the subsystems are capable of operating at respective ranges of clock frequencies, and wherein step a) includes supplying clock signals on N respective clock lines to the subsystems from a clock distributor at predetermined, independent clock frequencies within the subsystems' own respective ranges; b) selecting first and second ones of the N subsystems for communicating on the bus, wherein in step a) the first and second ones of the N subsystems are supplied their clock signals on their respective ones of the N clock lines, wherein the clock signal supplied to first one of the subsystems is a higher frequency signal than the clock signal supplied to the second one of the subsystems; and c) operating the selected ones of the subsystems during a communication interval at clock frequencies selected responsive to the ones selected, so that communication can occur at shared clock frequencies between the selected ones of the subsystems, including different shared clock frequencies for respective different pairings of the subsystems, wherein step c) comprises the steps of; c1) identifying a clock frequency range shared by the selected first and second subsystem; c2) selecting, from within the shared clock frequency range a single clock frequency for a transaction between the first and second subsystems during the communication interval; and c3) supplying a clock signal of the selected cloak frequency to the first and second subsystems by the clock distributor on the first and second subsystems respective ones of the N clock lines.