Plextor USA

Your PX-850A will operate with either the older 40-conductor cable or the
newer 80-conductor IDE/ATA cable. However, the 80-conductor cable
improves performance, and the PX-850A may not be able to write at
maximum speed (22X) without it. Although the new cable has 80 conductors
(wires), it still has only 40 connector pins, so it's compatible with the
connector on your PX-850A. (The extra wires are present to reduce
interference that would slow high-speed transfers.)