When Noctua release their new low-profile CPU cooler and asked us to test it out I really had to give it some good thought, after all its was made for small enclosures like HTPCs and the lower powered CPUs that they usually run.
Also they included a link for the TDP (Thermal Design Power) guidelines here.
The NH-L9i is a low-profile quiet cooler designed for use in small form factor cases and HTPC environments. While it provides first rate performance in its class, it is not suitable for overclocking and should be used with care on CPUs with more than 65W TDP (Thermal Design Power).
So that put me in a tight spot, as they say 65watts or less for either Intel Sandy or Ivy bridge cores.
They also add that anything more can be used but only with good case ventilation, and for the Ivy core you want to disable Intel Turbo Mode as well.
1) Our recommendations are based on an ambient temperature of 25°C or less. If your ambient temperature is significantly higher (30°C or more), we don’t recommend running the NH-L9i on 77W Ivy Bridge or 95W Sandy Bridge CPUs. For all other setups, please ensure good case ventilation when ambient temperature is 30°C or more.
2) Our recommendations assume that the cooler is installed in a typically equipped, properly ventilated HTPC system. If you are using particularly hot components inside your system, it may be necessary to use stronger case ventilation to ensure sufficient CPU cooling performance.
My HTPC rig is equipped with an Intel i7 3770K (Ivy Bridge CPU rated at 77 watts) and have an overclock from the stock 3,5Ghz to 4,2Ghz. Needless to say I was a bit skeptical how this would hold up against my massive Noctua NH-D14.