It is currently PCIe 2.0 on the x99 Classified. I am not honestly sure about speed, but that is the question I can answer.

Seems a shame the M.2 Slot is obsolete already for newer drives.
 
Thanks for the replies, confirmed what I'd thought, looks like an addon card, or stick with what I have.

It is the new retail version slight tweaks and it's own driver, rather than the OEM 951.
 
http://www.anandtech.com/...onsumer-vnand-nvme-ssd

Clockwork22
It is the new retail version slight tweaks and it's own driver, rather than the OEM 951.
 
http://www.anandtech.com/...onsumer-vnand-nvme-ssd

And it comes with a warranty unlike the OEM XP941 or SM951.

Kingston HyperX Predator SHPM2280P2/240G cost 320e in Serbia.
First that's insane price, second I don't know how they not shame to ask same price for far slower device than SM951 and 950 Pro.
SHPM2280P2/480G cost 590e in my town...speeds are 1400/1000 compare with Samsung 2500/1500.
I expect to find Samsung 950 Pro for about 300e 512GB version and I recommend to Kingston to little pay attention and become competitive or seriously to drop price on 120$ for their device. I didn't hurry... When I saw ex Samsung device I didn't want to invest in something bellow 2200/1400.
And looks like this two drivers 256GB and 512GB could be one of most wanted Samsung drives. I mean they sold really lot 840 and 850 SSD in my country. But they could repeat that with 950 Pro. I hear price are 256GB 200$ and 512GB 360$.
Only I never saw so big difference in speed between two different size and really worth invest immediately in 512GB.
Kingston used situation because no many drives on market and than start to sell M.2 30% faster than SATA III SSD and people hurry to buy like difference is 300%, only to connect first M.2 device no matter on anything but usually Samsung and Intel and leaders, weird that CORSAIR didn't done nothing.
And their M.2 will cost 50% more than Samsung.
 

Vlada011
Kingston HyperX Predator SHPM2280P2/240G cost 320e in Serbia.
First that's insane price, second I don't know how they not shame to ask same price for far slower device than SM951 and 950 Pro.
SHPM2280P2/480G cost 590e in my town...speeds are 1400/1000 compare with Samsung 2500/1500.
I expect to find Samsung 950 Pro for about 300e 512GB version and I recommend to Kingston to little pay attention and become competitive or seriously to drop price on 120$ for their device. I didn't hurry... When I saw ex Samsung device I didn't want to invest in something bellow 2200/1400.
And looks like this two drivers 256GB and 512GB could be one of most wanted Samsung drives. I mean they sold really lot 840 and 850 SSD in my country. But they could repeat that with 950 Pro. I hear price are 256GB 200$ and 512GB 360$.
Only I never saw so big difference in speed between two different size and really worth invest immediately in 512GB.
Kingston used situation because no many drives on market and than start to sell M.2 30% faster than SATA III SSD and people hurry to buy like difference is 300%, only to connect first M.2 device no matter on anything but usually Samsung and Intel and leaders, weird that CORSAIR didn't done nothing.
And their M.2 will cost 50% more than Samsung.
 

The Kingston was the fastest drive in it's day you can't really compare old models with new ones.
And there is probably no difference in daily use, probably see no gain, it's just that bug of wanting the latest carrot being dangled and look at the numbers hype :)

Vlada011
Off course if you update from Kingston M.2 to Samsung Pro you will not feel any difference except when you work something.
I doubt that difference is visible even between fastest SSD and M.2 but difference is huge in read/write.
You should wait this Samsung 950 Pro.  
If I need to choose between two similar device I love more Intel than Samsung but both made amazing hardware.
I hope this black label on 950 Pro could resist high temperatures...
Very rear I see some hardware and become priority to me as Samsung 950 Pro. 
 
http://www.samsung.com/global/business/semiconductor/minisite/SSD/global/html/ssd950pro/overview.html
 
 
 

Yes the Intel is a great drive, but twice the price and seems to be a bit picky bootwise from what I've read.
The Black label looks like it will be in the bottom of the case rather quickly, a cheap alloy heatsink with a logo would have been a better idea.
Just waiting on the Samsungs coming into stock, probably get one.

Why is the M2 slot on the classified only 2.0 speeds?

whitrzac
Why is the M2 slot on the classified only 2.0 speeds?

No idea but its unfortunate since at the same time most competitor boards if not all, all had 3.0 speeds.  The only way to get 3.0 speeds is to get an adapter card and use one of the PCI-E slots.

Yea I saw that later. Somehow I thought he need x8 speed.
I love Intel company more than Samsung. But for me M.2 speed transfer less than Gen 3 up to 32 is reason to change board.
I looked ASUS X99M-WS mATX and few people are interested for that board. In moment when they figure out that M.2 transfer is up to 10Gb/s big percent of people lose interest. From that moment I didn't visit that topic any more and read other stuff. 
As guy above say only chance is over PCI-E slot, but that exclude guys with i7-5820K because need processor where graphic card in first slot work on x16 even if other slots are occupied. That's i7-5930K and i7-5960X.
With i7-5820K when you Install Intel 750 graphic card work on x8 speed.

It's not problem...
Somehow I want to convinced myself that it's same but people don't like to see x8 speed today.
Price is similar 750 and 950 Pro, if I need to choose I will rather option with x16. 
Write speed on Samsung M.2 look much better, and that's not weird it's never device.
On Z170 is easier, chipset is enough to keep them on full speed and same will be on X190.
On Z170 have place for two Samsung M.2 950 Pro and two Intel 750 SSD and Sound Card and SLI on x8 or x16 if board have PLX Bridge.
 
This is best X99 combination and EKWB Supremacy EVO CPU block on Processor.