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Maximus VII Gene - PCIe lanes splitting when using a M.2 pcie ssd

czernobog
Level 7

‎04-24-2015 05:19 AM - last edited on ‎03-06-2024 03:08 AM by Community Admin

Hi,
I plan to buy one of the new M.2 PCIe 4-lane PCIe SSDs when they will be available.
Currently I have no other components on my mainboard, than the GPU (PCIe3 x16).
The system runs with a Intel 4760K (16 PCIe 3 lanes).
I've already read this:
http://rog.asus.com/forum/showthread.php?47497-PCI-Express-lane-allocation-on-ASUS-TUF-ROG-Z97-mothe...

My question is - do I have to sacrifice any internal components (SATA slots?) when I want to use the full capacity - 4 PCIe lanes - of the M.2 slot?
Another thing which is not really clear to me... When in PCIe mode, does the M.2 slot use PCIe v2 or is it possible to use a M.2 SSD with a PCIe v3 connection? How will the PCIe lanes be splitted then? If they are split (between the GPU and the M.2 slot) - is there a big performance drop to be expected from the GPU?
Thanks!
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mark0409mr01
Level 7

‎04-26-2015 08:41 AM

The M.2 slot on this board is capable only of pcie 2.0 x2 maximum, if you want to realise the full potential of a pcie 3.0 x4 M.2 SSD you would need to put it into the 2nd pcie 16x slot in an M.2 to pcie adapter. This in turn will limit the bandwidth to your first graphics card to 8x but will have little impact.

In short this boards M.2 slot is not really geard to the newer gen pcie 3.0 x4 SSD's if you want to utilise the M.2 slot get a Plextor m6e or understand that putting anything faster in the slot will limit its potential.
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czernobog
Level 7
In response to mark0409mr01

‎04-26-2015 10:59 PM

Thanks for answering.
So to get the max. potential of the SSD on the Maximus VII would be to put it on the PCIex4_1 slot (x2 speed), correct?
Are there any plans for the Asus boards to include a 4-lane M.2 slot in the next mainboard generation? Similar to ASRocks' "Ultra M.2" ?
e: I've already had two Plextor m6e, one was a DOA and the second one broke after a few weeks of usage, crashing the entire system daily. After opening a RMA case I had to wait 3 weeks for an answer to the status, luckily got a refund from the vendor. So for me it's never again Plextor.
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mark0409mr01
Level 7

‎04-27-2015 01:38 AM

PCIex4_1 slot is pcie 2.0 only and it shares it's bandwidth with the M.2 slot and mPCIe slots, depending on what you plan to install into these slots there will be a trade off. If you get a pcie 2.0 x4 M.2 SSD like the Samsung XP941 or Kingston HyperX Predator then it would perform best in the PCIex4_1 slot via an M.2 to pcie adaptor as it can run at up to 4x. If you install it into the M.2 slot it will never perform faster than 2x speed.

I think you will have to wait for skylake "Z170" or whatever it will be called if you want a board with pcie 3.0 x4 M.2 slot OR get X99 which has plenty of pcie lanes available. I believe the ASUS Maximus Impact VII has a pcie 3.0 x4 M.2 slot however this board is mITX only.
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czernobog
Level 7

‎04-28-2015 06:57 AM

I guess I'll hold off for now then with another M.2 SSD purchase, except if maybe I will find a x4 pcie SSD, like the one you mentioned, on sale. No other components except the SSD and GPU will be on the board, so I can dedicate all pcie 2 lanes to the SSD.
Thanks for the tip about the Maximus Impact board. Since I will put all my HDD's in an external enclosure this year and only the SSD and GPU remain on the mainboard, I will look into swapping my Maximus Gene for the impact in the next iteration:)
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