1. A method of verifying the passage of a data write across a bus comprising: at an originator, designating an echo return address; sending the data write from the originator across the bus to a target, the data write including a number of data entries and the echo return address; freeing the originator to perform other operations; receiving the data write at the target; at the target, counting the number of data entries in the data write received at the target with a counter; building a return echo write at the target, the return echo write including a count of the number of data entries received; transmitting the return echo write from the target across the bus to the echo return address; polling the echo return address from the originator to obtain the count of the number of data entries received at the target; comparing at the originator the count of the number of data entries received at the target with the number of data entries in the data write; and sending a verification to a host if the count of the number of data entries received at the target equals the number of data entries in the data write.