I dont think the 2mb or 8mb will affect the other drive.
The thing that will affect it is if one drive is an older, say, ata66 drive on the same cable with an ata133 drive.....they say that they both will run at ata66 speeds in that case.
of course i have heard that now it doesnt matter.
so I myself would like to see a definitive answer on this....cuz it does come into play if you put a DVD drive or cdrw on the same cable as a hard drive...cuz the cdrw's etc are usually ata66....so it would be nice to know if the cdrw is slowing the faster hard drive down.
Any benches or definitive articles out there??