Thank you for this guide! I took heavy inspiration from it, however I was unable to get the Frozn A400 cooler anywhere here in Germany, which is why I went with the Thermalright Assassin King 90 because it appeared similar in mounting hardware and dimensions and wasn't very expensive either (€19).
One advantage of the Thermalright is certainly the fact that it has a solid copper baseplate, so no copper shims are needeed to spread the heat from the CPU die onto all the heatpipes of the cooler (but careful, Thermalright has many similar coolers and the King 90 appears to be the only one with that particular feature). However, it turns out that the Thermalright is ever so slightly too wide, so I ended up having to grind away most of the protruding part of the fins where the fan mounting brackets are supposed to clip onto on one side of each cooler. Also, while the included mounting hardware does include "knurls" similar to the ones of the Frozn A400, they do in fact not screw onto the pegs that Apple uses to hold the CPU cards in place, so I had to figure out what threading these actually use (it's M3.5, which explains why nothing "normal" would fit) and then order some M3.5 thumb-nuts from China since I was again unable to find any for sale locally. One thing to note here though: Apparently, M3.5 is a screw size that was commonly used for mounting Intel LGA2011 coolers, so if you have an old PC cooler (or at least its mounting hardware), then there
could be a M3.5 knurl included with it.
Another thing I had to keep in mind because of my approach is to raise the mounting bracket on the side with the knurls to match the height of the one on the other side as much as possible, as that way you are much less likely to accidentally crack your CPU die due to uneven pressure - I did this by purchasing a pack of 1mm thick plastic washers and stacking them. In your original guide, this happens automatically because of the knurls not screwing down all the way.
But anyway, I now have a cool and quiet G5 quad that I (hopefully) won't have to service again. Idle temperatures now hover around 30c (at about 20c ambient) and I haven't seen more than 65c under load, even when running synthetic loads like Geekbench 2 or Cinebench 11.5, which in both cases is at least 10c less than previously with the LCS! It's Geekbench 2 32-Bit Score is 3272 and the Cinebench 11.5 score is 1.99 by the way, in case anyone's interested. Temperatures under normal (non-synthetic) load usually hover around 50-55c.
For future reference, I assume that any cooler using the same style of mounting hardware and identical (or smaller) dimensions should work the same - I was originally thinking about buying the Noctua NH-U9S as it was the only other similarly sized cooler I could find with a solid copper baseplate, but given that it appears to be at least 1mm wider than the Thermalright I'm glad that I didn't - can you imagine grinding away at a €70 heatsink?
