I have this
Note the clips, this is revision A with a mounting different from rev. B, and is not compatible with AM2.
I add this
Then I get this
As you can see even when fanless the Ninja still cools better than an AMD stock cooler screaming away at 4000rpm. Just using a fan even if it's a low speed one would increase the cooling performance many times. If the temperatures are to be believed, my X3 720 is idling at the temperature of the surrounding air.
The Pentium 4 was the first (?) platform to use big-ass stock and aftermarket heatsinks, and while CPUs have undergone at least one socket change the powerful coolers of the Pentium 4 era are still, erm, powerful enough to cool the current cooler-running CPUs. It's a waste to see them go to waste, so Thermalright AM2 RM (Rev.B) to the rescue. Use Pentium 4 coolers on AM2/AM3 CPUs. There are also solutions for K8 and LGA775. We just need to wait for LGA1156.