Abstract: A bus control interface selectively and transparently couples a bus agent to a cache and to a memory to provide transparent burst access to addressable data having a portion residing in cache and a portion residing in memory. The bus control interface steers transactions to the cache or to the memory depending on where the data resides. In this way, the bus control interface supports, without a disconnect, burst read transactions that cross cache line boundaries. The bus control interface also supports bus watching single-word read (and write) transactions as well as burst write transactions.

Abstract: An apparatus and method is provided for precharging a conductor within a bus containing a plurality of conductors. The apparatus comprises a precharge circuit which drives an intermediate voltage between VDD and ground upon respective conductors. The precharge driver maintains the intermediate voltage within a range between a first voltage level and a second voltage level, the second voltage level being higher in magnitude than the first voltage level. The precharge voltage defined within an intermediate voltage range is chosen to consume minimal power within the precharge driver. An isolation device can be provided on each conductor for isolating the intermediate, precharged value from a receiver circuit input so as to minimize power consumption of the overall circuit. Precharging to an intermediate value causes logic-driven transitions within the bus to occur at a faster frequency than if the bus were precharged to full rail.

Abstract: A driver circuit is provided which unconditionally discharges a bus conductor during clock cycles in which the driver circuit is transmitting a value. The unconditional discharge occurs during a first drive phase of the logic drive state. During a second drive phase, the driver circuit either charges or continues to discharge the conductor based on the data value being transmitted. Since the conductors are transitioning in the same direction at approximately the same rate, line to line coupling is virtually non-existent during the first drive phase. By partially discharging bus conductors during the first drive phase, transition speed is increased to the point at which a receiving circuit senses the transmitted value. Effectively, the line-to-line coupling which would have occurred during the first drive phase is endured during the second drive phase, when certain conductors may be recharged.

Abstract: An apparatus is provided for precharging a conductor within a bus containing a plurality of conductors. The apparatus comprises a precharge driver which precharges alternating pairs of conductors to opposite rail voltages. By precharging pairs of conductors to alternating rails, the present apparatus can minimize the speed degradation problems associated with a transitioning target conductor within the bus. Precharging alternating pairs of conductors also minimizes crosstalk noise from transitioning neighbor conductors to a non-transitioning target conductor. The improved dynamic bus thereby demonstrates improvements in speed degradation and crosstalk noise as seen by a transitioning target conductor or non-transitioning target conductor, respectively.