1. In a computer system having a first processing unit, a second processing unit, a memory bridge, a system memory, and a bus that connects the second processing unit to the first processing unit, the memory bridge, and the system memory, a method for processing a read or write request at a second processing unit, comprising the steps of: receiving a read or write request at the second processing unit over a first virtual channel of the bus; generating one or more derivative read requests at the second processing unit while processing the read or write request and transmitting the derivative read request to the system memory over a second virtual channel of the bus; and receiving a completion of the derivative read request over the second virtual channel of the bus and completing the original received read or write request.