The important thing to know is that the Coppermine core is better and that's the one you should buy. Just make sure that the processor you buy will fit in the motherboard. The Katmai PIIIs are Slot1 CPUs. The early Coppermines are also Slot1, but the newest Coppermines come in Socket370 only. So when you order one make sure your getting the right one for your motherboard.