Maximus XI Extreme & 2x 2080 Ti Matrix NvLink

[Zka17]

The Rampage VI Extreme seems to have the best PCIe spacing for the 3-slot cards - but they still will be pretty close to each other! Specifically if you intend to use a case with vertical mounting of the motherboard... in case of horizontal mounting, you may be OK because of the different heat dissipation path.

Regarding the 9980XE CPU, that's an 18-core beast! Meaning that the base frequency and the potential max frequency will be low compared to a CPU from the same class, but lower core count.

I don't think that many games would benefit of 18-cores... but most of them certainly would suffer of lower clocks... - that's if the game is CPU intensive, some of them are using more GPU, so there you wouldn't have issues with two 2080 TIs...

looking at your original config, I would keep the 9900k on a Maximus XI Formula or Extreme, drop the RAM to 32GB, and ditch one of the Matrix cards... that system would chew through everything you throw at it in terms of gaming... - but in terms of airflow around double 3-slots cards, just keep in mind the possibility of horizontal motherboard placing...*

[Antrix]

drop the RAM to 32GB

Can you explain me this moment please?

[Zka17]

Sure: if you want a gaming rig, then having 64GB of RAM may just complicate things... more RAM harder to OC (even to the XMP settings). I assume that you want to OC the 9900k - the best chance is to not stress too much the IMC (internal memory controller). The IMC is stressed more with the amount of sticks you have, hence I went for half of a 64GB kit - use only two sticks of 16GB. If you really are going for high memory frequencies with low timings, then you actually don't want more than 2x8GB sticks... For pure gaming purposes, even 32GB is overkill...