AMD's 4,094-pin socket, which is paired with the X399 chipset for Threadripper, is massive by any measure. AMD christened it as Socket TR4 (SP3r2) for consumer motherboards and Socket SP3 for EPYC servers. The physical dimensions of both LGA (Land Grid Array) sockets are identical.
In either case, Socket TR4 far outweighs Intel's 2,066-pin socket for the X-Series platform, which has the natural side effect of a much larger heatspreader on the Threadripper processors. That presents challenges for cooler vendors, but AMD also uses indium solder under the heatspreader, which should help thermal performance significantly.
We know that AMD and various cooler manufacturers will be offering special solutions that will allow existing coolers to be used on AMD's much larger Socket TR4. We succeeded in obtaining a set of new adapters for the Alphacool XPX that we use in our German test lab. Please note that the manufacturer did not serve as a source for our exclusive schematics.
Since we now have the complete design drawings for the socket, we have superimposed the cooling solution over the socket schematic and made some educated guesses. This helps us to assess compatibility beforehand.
It's striking that, in addition to the rectangular shape of the CPU recess in the socket frame, there is an asymmetrical arrangement of the mounting screw emplacements. On the left, we see a distance of 65.2mm and to the right only 46mm. We also see very nicely where the modified square (or round heatsink) cooler will mount. A large, rather square waterblock, like the illustrated Alphacool XPX, should be an advantage over the round solutions we find on many of the Asetek products.
The rectangular heatsink covers about 90% of Threadripper's integrated heat spreader after accounting for the screws on the waterblock and the uncovered edges of the processor. Also, the arrangement and size of the microchannels inside the waterblock are, of course, not (yet) optimal. Threadripper CPUs have four die, and thus there are large disparate hotspots. This requires large-area microchannel fields and other flow profiles in the cooler.
For the launch, however, the water block should be sufficient, though it isn't perfect yet. We are curious when (and which) products will be specially adapted for the TR4/SP3r2 socket, and how much better they will perform.
For those of you do-it-yourselfers with a CNC milling machine, or for those who are simply curious, we have compiled all of the relevant design documents and present them below.
Socket SP3 front side