Originally posted by Chriso
That's exactly what I just said!!!
I think the confusion is in the way you typed it although you may know the answer to this. One can misinterpret what you typed by thinking that having more than one device per IDE channel degrades performance for each device.
"When having two devices sharing one channel (primary or secondary) you will see a drop in performance. This is due to the fact that the IDE channel only send one command at a time which often causes one of the drives to be forced to wait."
This is not true in the event you have two HDD(obviosuly not a very old one <ata33) but lets say two ata100's, there would be less than 1% drop in data transfer speed. If you have 1 HDD and 1 Optical on the other hand, the HDD will always drop its speed to that of the optical drive and thus be lowered significantly(close to ~33% drop in transfer speed.
Hope that clarified things up.