Raster operations unit with interleaving of read and write requests using PCI express

摘要

A raster operations (ROP) unit interleaves read and write requests for efficiently communicating with a frame buffer via a PCI Express (PCI E) link or other system bus that provides separate upstream and downstream data transfer paths. One example of a ROP unit processes pixels in groups, performing read modify writeback sequences for each group. The read requests associated with pixels in a second group are advantageously interleaved with the writeback requests for pixels in the first group prior to sending the requests on the system bus.