In this PC both drives on one channel with the hard drive using the other channel. Using
nero I found that the top buffer remained at about 50% and the lower buffer fluctuated madly.
I do have other machines - one with sata but nero not loaded - so that is why I used the older machine. when I get time I will install Nero and try again on the P4 3.2 2 sata drives BenQ1655 and Liteon 1693S. One this machine each burner is on its own channel.