Computer system which switches bus protocols and controls the writing of

Abstract

An electronic computer which uses different bus protocols to transfer information for processor-to-processor communication and for processor-to-peripheral communication. The electronic computer includes an address buffer translator which translates a virtual address to a physical address and produces a bus protocol specifying signal. A bus interface changes bus protocols in accordance with the bus protocol specifying signal in order to permit a transfer of a physical address and data on the bus. In another embodiment, when the data in a cache memory is changed, a dirty bit for the cache memory is set but a corresponding dirty bit in the address translation buffer is not changed until a copy-back operation from the cache memory to a main memory occurs. The dirty page bit of the address translation buffer is changed utilizing software.