PC Stats posted a review on the Zalman ZM-NBF47 Northbridge Chipset Heatsink

One of the problems with old motherboard chipset heatsinks, apart from their small size, is the little fans almost always seize up. Constant use, time, and dust bunnies conspire to stop impeller blades from spinning. If the fan stops on a postage size heatsink, there's a good chance the chipset will overheat - there's just not enough surface area to adequately release the heat from the chipset into the surrounding air. For this problem Zalman have introduced the ZM-NBF47 fan-style chipset heatsink.

Zalman ZM-NBF47 Northbridge Chipset Heatsink Review