Overl0rd from the forum here thanks for the shout out at the beginning @LinusTech, I’m happy to have been of assistance Awesome that this obscure platform is getting some love again!
A couple of points I would like to mention:
-While the QX9775 CPUs are the most awesome way to go on this platform. It will work just fine with regular 771 Xeons and back then a TON of people went that route. The board will also work just fine with a single CPU. Especially the CPUs with a 1333MHz FSB have great OC headroom (as 5400 chipset runs out at around 430MHz bus speed) and could potentially reach beyond 4GHz. Overclocking the QX9775s is rather straightforward, mine do 4GHz at 1.41V. Just make sure to have proper cooling on not just the CPUs, but also active cooling on the north bridge and the FBDIMMs; those will get up to around 90C.
-Despite the fact that the drivers of the Nforce 100 chips are troublesome in Windows 10, SLI should work fine using PCIe 2 and 4 (I have tested this personally). The problems are less under Windows 7, but still present.
-16GB of RAM is definitely supported out of box. I personally run 4x4GB 667MHz overclocked to 800MHz. To do this you do have to have the latest BIOS version, as more memory config options were only added later on.
For those interested in some comparative testing and further information, on my Youtube channel (Dellchannel21) I have a lot of videos covering this platform in detail.
In short; it still holds up reasonably well in gaming considering the age of the microarchitecture and having that extra CPU now definitely make a difference. It of course won’t be a valid option for a 144Hz setup, but in somewhat older titles it is playable. Crysis 3 was the best example of the extra cores really kicking in. This was tested with a GTX 1060 6GB in 2018.
SKULLTRAIL GAMING - How does Intel's $4000 Overclockable Dual Socket system perform?
For how it compares to under synthetic benchmarks; here I clocked both QX9775s to 4.2GHz with 16GB 800MHz CL5 memory and it was still really impressive. Beating the 5GHz FX 9590 Bulldozer and coming very close to the stock Skylake 6700K.
OVERCLOCKING SKULLTRAIL - Dual QX9775 over 4GHz
For how the latest and greatest games do, well… you can actually sort of play Battlefield V 64 player and I’m extremely impressed that was possible.