I came across this post from google, and thought I'd update it in case anyone else does as well.
Jahntassa is correct that the purpose of an 80 pin cable is to insert ground lines between data lines, to reduce inductive crosstalk between the lines (basically two long wires in parallel can act like antennas broadcasting weak signals to/from each other). The higher the frequency of the signal on the line, the stronger the crosstalk. For high-speed IDE controllers the crosstalk can be bad enough to interfere with signal. The speed of the platters (5400, 7200 RPM) makes no difference - just the signaling rate (ATA/33, 66, 100, 133, etc). This is absolutely not a problem with ATA/33, especially when you are using such short cables. If you buy a 2-6" 44pin cable you don't need to worry about crosstalk on a ATA/33 or 66 drive.