Both the P965 and newer, slightly tweaked 975X chipsets feature essentially a memory controller upgrade. The major feature is support for 800MHz (PC 8000) memory. In addition, Intel's Fast Memory Access system means the north bridge can monitor every pending read or write request and rearrange the order to maximise efficiency. It can also perform writes to memory on-the-fly, slotting write requests in between the higher priority read requests. This is preferable to queuing write requests and flushing the queue periodically, which renders the memory inaccessible until the flush is complete.