FrostyTech posted a review on the Zalman ZM-NB47J Passive Northbridge Heatsink
A quote from the article:
Zalman ZM-NB47J Passive Northbridge Heatsink Review
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 too. For this problem Zalman have introduced a small passive aluminum chipset heatsink called the ZM-NB47J.
Zalman ZM-NB47J Passive Northbridge Heatsink Review