Most people would imagine that the NH-L9i and the NH-L9a are the same and only the socket compatibility differs; however, that is wrong. Even though both coolers are physically similar, the NH-L9a is longer than the NH-L9i by a full 2 centimeters.
Looking at the base of the coolers, we could not help but notice that the installation retention brackets can be interchanged between the two coolers. Instead of making a universal cooler for both sockets however, Noctua decided to make the AMD cooler slightly larger and go with socket-dedicated designs.
The many small fins of the coolers are soldered on the nickel plated heatpipes and interconnected to each other, creating a mechanically solid and visually appealing product. Noctua is careful when it comes to quality and thus no edge or corner is excessively sharp.
Both are making use of the same low profile NF-A9x14 92mm fan, featuring Noctua's proprietary SSO bearings, anti-vibration pads and a maximum rotational speed of 2200RPM. The company supplies screws for 25mm fans but these are not included and would increase the height of the coolers significantly.