Kwai C So

58570853, Jan 5, 1999

Nov 13, 1996

8/746645

Lei L. Zhang - Newark CA
Kwai Chuen So - San Jose CA

Cypress Semiconductor Corporation - San Jose CA

G06F 1300

395309

A host bus interface device is provided for interfacing a processor coupled to a host bus to XT/AT legacy I/O devices and a high speed bus. The legacy I/O devices include an interrupt controller, timer/counter and a real time clock. The host bus interface includes a host controller coupled between the host bus and the high speed bus, with the interrupt controller, the timer/counter and the real time clock coupled to the host controller. The host controller is configured to provide an interface between the processor coupled to the host bus and the interrupt controller, the timer/counter, the real time clock device and the high speed bus. The novel host bus interface device has the advantage of improving system performance of an XT/AT compatible personal computer by reducing access latency of the processor to the XT/AT legacy I/O devices.

58225455, Oct 13, 1998

Oct 29, 1997

8/960585

Kwai Chuen So - San Jose CA

Cypress Semiconductor Corp. - San Jose CA

G06F 1502

395280

A method and apparatus for eliminating all unnecessary switching/toggling of bus signals is provided. A first circuit that is coupled to a first and second bus is provided. This first circuit selectively couples (i. e. , transparently passes) a first signal from the first bus to the second bus in response to a control signal. A control/decoder circuit, coupled to the first circuit, generates the control signal based upon whether or not a bus cycle on the first bus is directed to a device coupled to the second bus. If the address is directed toward a device coupled to the second bus, the present invention transparently passes the bus signals on the first bus to the second bus. If not, the control/decoder circuit instructs the first circuit not to propagate the bus signals from the first bus to the second bus. In other words, the value of the bus signals on the second bus are unchanged.