Well, the motherboard decision locked me into just a few generations of CPUs from Intel’s Core-X lineup. If I had my choice I think I would have preferred going with something with lower TDP and wattage options like the AM4 board that I found but didn’t have or if I could have found any mainstream Intel option. X299 isn’t all bad though, it has a lot of PCIe lanes with most of the options and I had a few different options on hand. I have the i7-7740 on hand which was a Core-X version of the i7-7700K, but as it turns out it isn’t listed as supported on the EVGA X299 Micro.
From there the options I had on hand were the higher end i9-7980XE, the i9-7960X, and the i9-7900X. I could just go with the big 7980XE with its 18 cores, but I am a little concerned that it will cause heat issues in the build. I will talk about cooling here shortly but taking to cool anything in the limited height that a 2U case offers can get complicated. Servers designed for it integrate cooling solutions that use the full case airflow for cooling and the RM21-308 does have three 80mm fans. But my experience with SFF builds is to never trust any cooling. So I was looking at the i9-7960X and the i9-7900X. The 7960X has the same TDP officially as the 7980XE but with 16 cores I have decided to give it a try. If it doesn’t work out, the 7900X will be my backup plan because it has a “lower” 140-watt TDP. But getting the extra 6 cores was worth a try.