[SOLVED] Is ultra m2 designed to work with x16 pcie video cards

[raknarius]

ASRock Ultra M.2 limiting video card?

ASRock Extreme6AC motherboard and Radeon R9 ....280 I think? Intel i7-4790K CPU. Looking to add a Samsung 970 Evo NVMe PCI-E SSD into the Ultra M.2 slot. From all I've read, that Ultra M.2 slot shares in the 16 PCI-E lanes and SLI is no longer possible. That's fine. I'll never SLI this machine...

forums.tomshardware.com

The above thread doesnt really answer this. Im thinking if its designed to use pci lanes right off the cpu, as long as the chipset has enough lanes to fullfill the 4 lanes for ultra m2 and x16 for the pcie video card, aka 20 lanes we should be good, or are lanes also dedicated to other parts of the computer like usb, ssds, sata. etc.

I want to build a gaming rig but the last thing i want to do is limit it to x8 for a ultra m2.

 

[Obakasama]

I'm not aware of any motherboards where the U.2 port disables the primary PCIe x16 slot. You're looking for a general answer to a large variety of possible configurations of CPU and motherboard chipset. My AB350 Pro4 U.2 port (so to speak) disables the second x16 slot, and has nothing to do with the primary x16 slot.

I would suggest you look to the CPU and motherboard specs of those components which you want to use for a more nuanced answer.

 

[popatim]

Plugging in a M.2 adapter into a pciex16 slot may drop the GPU slot to x8 mode depending on the motherboard.

Since your motherboard has no M2 slot then this is indeed the case.

- 3 x PCI Express 3.0 x16 slots (PCIE2/PCIE3/PCIE4: single at x16 (PCIE2); dual at x8 (PCIE2) / x8 (PCIE3); triple at x8 (PCIE2) / x4 (PCIE3) / x4 (PCIE4))

The reduction to x8 lanes should not lead to a noticeable slowdown of your GPU though. Ie - you'd likely only see it in benchmarks.

 

[raknarius]

But if your using a designated m2 slot, that uses pcie lanes x4, does that drop your gpu to x8?

 

[TJ Hooker]

Is this your motherboard? https://www.asrock.com/MB/Intel/Z97 Extreme6ac/index.asp
If so, it's pretty clear about how it works:

"If M2_1 slot is occupied, PCIE2 slot will run at x8 mode
[...]
Ultra M.2 Socket (M2_1)"

 

[raknarius]

So thats pcie2 slot, so does that mean pcie1 slot still runs at x16

 

[popatim]

I guess you didn't understand my post.

ALL of your x16 slots share the PCIE lanes.
If you have installed your GPU and install any additional PCIE cards then YES your GPU will drop down to x8 mode regardless of which slot you use..
Will you notice this? - Only in benchmarks.

 

[ElectrO_90]

I am sure you wouldn't notice any difference between 8x and 16x, but it won't go down if you install exactly what you said, 1 M2 and a GPU. 20 lanes is fine.

 

[TJ Hooker]

So thats pcie2 slot, so does that mean pcie1 slot still runs at x16

Maybe try reading the specs page? PCIE2 is the primary x16 slot.

"2 x PCI Express 3.0 x16 Slots (PCIE2/PCIE4: single at x16 (PCIE2); dual at x8 (PCIE2) / x8 (PCIE4))"

 

[TJ Hooker]

I am sure you wouldn't notice any difference between 8x and 16x, but it won't go down if you install exactly what you said, 1 M2 and a GPU. 20 lanes is fine.

If the OP uses the Ultra M.2 slot (M2_1) as they intend, the primary x16 slot would drop down to x8.

 

[raknarius]

lol so confusing i dont think ill ever get an answer

 

[ElectrO_90]

lol so confusing i dont think ill ever get an answer

What is more confusing is that you are taking a reference from a motherboard thats 5 years old.
Are you planning on building a computer based on an 5 year old motherboard?
If you are, then you will have the 8x issue
if you are not, then don't worry about it and stick with AMD

 

[raknarius]

i didnt pick a motherboard yet, im looking at modern motherboards with the ultra m2 slot

 

[ElectrO_90]

i didnt pick a motherboard yet, im looking at modern motherboards with the ultra m2 slot

So the reference you are comparing it to, which is why you and the rest of us are confused has nothing to do with the system you will buy?

 

[TJ Hooker]

lol so confusing i dont think ill ever get an answer

i didnt pick a motherboard yet, im looking at modern motherboards with the ultra m2 slot

You have a very clear answer for the specific motherboard you implied you were looking at. Not that that answer is useful anymore now that we know you have no intention of getting that motherboard.

"Ultra M.2" appears to just be ASRock's term for a PCIe 3.0 x4 M.2 slot. That used to be a somewhat special thing, but now it's the norm. For any modern motherboard*, you will have no issue using a single PCIe 3.0 x4 SSD and still having your graphics card run at full x16 bandwidth. Intel motherboards will have the M.2 slot connected through the PCH (which doesn't share bandwidth with the primary PCIe x16 slot), and AMD motherboards use a x4 connection from the CPU that's dedicated for M.2 storage (so it too does not share bandwidth with the primary PCIe x16 slot).

*With AMD, you'd need to get a Ryzen CPU/APU. With an Athlon, you'd only get PCIe x2.