Intel CONTROLLERS 413808 - Manual (Page 402)

Intel
®
413808 and 413812—Messaging Unit
Intel ® 413808 and 413812 I/O Controllers in TPER Mode
Developer’s Manual October 2007
402 Order Number: 317805-001US
4.2.1 Transaction Ordering
From a PCI standpoint, the Messaging Unit is a piece of the ATU and therefore must
maintain ordering requirements against ATU transactions. Transaction ordering is
achieved for the Index Registers, the Doorbell Register, and the Message Registers
since these transactions are routed through the standard set of ATU read/write queues.