Apple argues that such big heatsink can reduce the air flow required to cool them down, contributing to a more silent Mac Pro.
To try confirming this assumption, we have asked Dane-Elec to lend us 4 FB-DIMM RAM modules of 1GB RAM, featuring standard heatsink.
On the top is the Dane-Elec module (Samsung), and on the bottom is the Apple original FB-DIMM module with its larger heatsink.
We have installed them over one week in a Mac Pro 3.0GHz in addition to the 4x1GB original FD-DIMM modules from Apple.
We have installed the Dane-Elec modules in order to ensure their use during operations (8GB of RAM is a lot, and a Mac Pro does not really need them all in 100% of the time).
We have extensively used the machine during this week of testing, and we could not notice any increase of the fan rotation speed. We have used Hardware Monitor to confirm our evaluation, with or without the Dane-Elec modules fans #1 and #2 spins at 500rpm whereas fans #3 and #4 at 600rpm.
When assessing the temperature of the RAM module heatsinks, we could notice that it was slightly warmer for the Dane-Elec modules but nothing dramatical.
So, you do not really need to order your RAM modules from Apple USA.
