There are two version of the Ultra-90, one for Intel S775 comes with push pins and can be freely rotated in any direction, installation is plug and play. The S939/AM2 version comes with a separate mounting clip which allows you to install the Ultra-90 in only one direction which is directly related to your socket orientation. On my DFI NF3 250Gb motherboard this leads to a less then optimal configuration, as the heatsink is not pointing towards the rear of the case. Optional Extra: S Mounting Clip
Luckily Thermalright has recently released the S-clip, as the name implies, it's a mounting clip for Ultra-90 and HR-01 in the form of an S which allows you to freely orientate the heatsink on the S939/AM2 bracket. Installation is slightly different from what you might be used to, there is spring in the middle which pushes a pin down onto the heatsink's base, of course there is a weight limit using this method, probably the reason why the Ultra-120 is not supported by this S-clip.
I've tested the Ultra-90 with the normal and S-clip, in the optimal configuration the temperature results on the CPU were ~2?C lower, not too bad in a low airflow enclosure.
Onto our test setup ->