This item is from the Yet Another Enhanced IDE/Fast-ATA/ATA-2 FAQ, by John Wehman and Peter den Haan with numerous contributions by others. (v1.92).
This should work fine.
Older drives do not support the high-speed advanced transfer modes defined by ATA-2 and, later, Ultra-ATA. To retain compatibility with these drives, ATA-2 and Ultra-ATA interfaces have programmable timing. The driver or BIOS queries the drive regarding its maximum transfer rate and will configure the interface to match. A few interfaces are jumper configurable in which case the responsibility is yours.
If you intend to put an older drive on the same cable as an ATA-2 drive, you may want to verify that your interface is capable of using independent timing for master and slave device. Otherwise, your old drive might end up slowing down your newer one because the controller is forced to use the lowest common speed. Modern interfaces like the Intel PIIX3 (430HX and VX and 440FX chipset), PIIX4 (430TX chipset) and, to a lesser extent PIIX (430FX chipset) don't suffer from this problem.