Detecting and flushing maximal length packets is set forth herein. In one embodiment, the method comprises receiving a flushing event and, in response to the flushing event, repeatedly detecting a maximum length packet of write data from a write combining storage area and flushing the detected maximum length packet to a target input/output (I/O) device over a bus. Each maximal length packet is a packet of maximum payload of write data that can be formulated within in the write combining storage area while adhering to packet protocol rules for the bus.