Method and apparatus for prefetching data read by PCI host

摘要

Write posting buffers and read prefetch buffers are arranged in an integrated multiport switch between a PCI interface and an external memory interface. When a PCI host initiates a PCI transaction to write data from an external memory, the data provided by the PCI host is written into the write posting buffers. Then, the contents of the write posting buffers is transferred to the external memory. The read prefetch buffers are used to temporarily store data prefetched in anticipation of a PCI transaction initiated by the PCI host to read that data from the external memory. When the PCI host initiates the read transaction, the address of the requested data is compared with the address of the prefetched data to transfer the prefetched data to the host if a match is detected. In an auto-prefetch mode, data is automatically prefetched from the external memory when an extension bus port output queue contains a frame pointer for a frame queued for transmission over the PCI interface to the PCI host.