Mechanisms for improving the efficiency of bus-request scheduling are provided. In a read-write segregation mechanism the type of a selected entry in a buffer is determined. If the type of the selected entry matches the type of the last issued entry, or if there are no further entries in the buffer that match the last issued entry, the request is issued to the system bus. A temporal ordering mechanism associates a request sent to a buffer with an identifier, the identifier designating a time at which the request was originally generated. The request identifier is modified when a prior request is issued, and thereby reflects a history of prior issuances. A request is issued when the historical information recorded in the identifier indicates that the request is the earliest-issued pending request in the buffer. A third mechanism for increasing the efficiency of bus request scheduling in a buffer includes segregating lower priority cache eviction requests in a separate write-out section of the buffer. Request entries in the write-out section are issued to a system bus only when there are no pending entries in a bus queue.

A data transmission sequencing method is disclosed. A data read operation from a primary bus to a secondary bus can be executed without having to wait for the complete transfer of write data stored in posted write buffer transferring to the primary bus, as long as the secondary bus is not in use. In the mean time of the primary bus issues a read operation to the secondary bus, the secondary bus can issues write operation to the bridging device when the secondary bus is not in use. Similarly, there is no need to wait for the completion of read operation. With this type of data transmission sequencing mechanism, idle sessions in a conventional transmission sequencing method are eliminated leading to a higher data transmission rate.

A method of and apparatus for improving the efficiency of a data processing system employing a multiple level cache memory system. The efficiencies result from managing the process of flushing old data from the second level cache memory. In the present invention, the second level cache memory is a store-in memory. Therefore, when data is to be deleted from the second level cache memory, a determination is made whether the data has been modified by the processor. If the data has been modified, the data must be rewritten to lower level memory. To free the second level cache memory for storage of the newly requested data, the data to be flush is loaded into a flush buffer for storage during the rewriting process.

A non-volatile memory is described that utilizes a cache read mode of operation, where a next page of memory is being read/sensed from the memory array by the sense amplifiers while a previously read page of memory is being read from the memory I/O buffer, wherein the next page is user selected. This random cache read mode allows for a memory with a random page read capability, in which the address of the next page of data to be read is user selectable, which benefits from the low latency of a cache read mode of operation due to concurrent data sensing and data I/O.

A non-volatile memory is described that utilizes a cache read mode of operation, where a next page of memory is being read/sensed from the memory array by the sense amplifiers while a previously read page of memory is being read from the memory I/O buffer, wherein the next page is user selected. This random cache read mode allows for a memory with a random page read capability, in which the address of the next page of data to be read is user selectable, which benefits from the low latency of a cache read mode of operation due to concurrent data sensing and data I/O.