New Haswell build in Post Your Pit Test Results Posted October 29, 2016 · Edited October 29, 2016 by terry1966 but every time I changed the overclock settings it would not boot up - couldn't find the OS. sounds weird, you have any ideas about why? is it a motherboard specific issue or is it because while ocing you're also ocing the pci-e lanes? maybe a uefi update might solve the issue, must admit i can't see why you should have a problem if the oc was stable and can only think it must of been a timing issue with the controller on the nvme drive some how. seems lots of people oc and use nvme drive with no problems judging by this topic. :- http://www.overclock.net/t/1603995/samsung-sm961-nvme-thread/30 you got to admit though 1 nvme drive being faster than 6 ssd's in raid 0 is mighty impressive and why i'm definitely going to have one myself in my next build, i was so impressed with my daughters build i really really didn't want to give it to her (course i did though.). i ran across this while seeing if i could find out why you were experiencing problems when ocing. The problem turned out to be something as simple as our overclock settings. We use Corsair Vengeance LPX DDR4 modules rated at 2,800MHz, and we were using their built in XMP profile for our system's overclock. However, this automatically sets the base clock to 125MHz, which is a requirement when using high frequency memory (i.e. above 2,666MHz) on X99. However, this also affects the speed of other parts of the CPU, not just the cores, and one of those parts is the onboard PCI-E Gen 3.0 controller. In turn, in order to maintain PCI-E stability at this clock, our motherboard was downgrading the PCI-E interfaces to Gen 2.0. You can force the graphics slots back to Gen 3.0, but there's no such option for the M.2 slot, which makes sense since storage devices require perfect stability. We have not been able to confirm exactly how other motherboard manufacturers handle the situation, but it's probably safest to stick to 2,666MHz DDR4 on X99 when using a PCI-E 3.0 storage device. It should also not be a problem on Z170, where the PCI-E controller's clock is separate to the CPU BCLK. http://www.bit-tech.net/hardware/storage/2015/11/11/samsung-ssd-950-pro-review/1 so your problems were more than likely due to the bclk over 100MHz on x99.