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donalgodon · ‎05-14-2018

If the user installs an M.2 drive in the upper slot closest to the CPU, the graphics card runs at 8x instead of 16x.

This seems like poor design, given that the heatsink is installed by default on that M.2 slot. It would lead the average person to assume it is the primary M.2 slot, but it seems to be the lower slot.

Will running a dual M.2 setup lower the performance of my graphics card?

I've seen users complain of stuttering in games until they moved their M.2 to the lower slot.

brkkab123 · ‎05-14-2018

The top m.2 slot that has the heat-sink on it does use PCIe lanes.
If you use it your x16 PCIe slot will only use x8 speeds.
m.2 slot 2 on the bottom doesn't use PCIe.
If you have a single m.2 ssd use the lower m.2 slot for it.

schweigert · ‎05-15-2018

brkkab123 wrote:
The top m.2 slot that has the heat-sink on it does use PCIe lanes.
If you use it your x16 PCIe slot will only use x8 speeds.
m.2 slot 2 on the bottom doesn't use PCIe.
If you have a single m.2 ssd use the lower m.2 slot for it.

wow..... thanks for this info. I was going nuts, figuring out why my card was only at 8x

now i wonder whats the net best config --- m.2 using pcie lanes w/ card at 8x. or m.2 using the bottom mount non pcie but card at 16x?

gorpo · ‎05-15-2018

schweigert wrote:
wow..... thanks for this info. I was going nuts, figuring out why my card was only at 8x

now i wonder whats the net best config --- m.2 using pcie lanes w/ card at 8x. or m.2 using the bottom mount non pcie but card at 16x?

Use the bottom M.2 slot (M.2_1). It's PCIe X4 too, directly to the CPU. https://youtu.be/S0mR4IoNWkQ?t=3m20s

This is one nice and unique feature of the C7H. As far as I know, it's the only board that allows 2 M.2 operating at PCIe X4. I think all other motherboards have any second slot sharing lanes with other I/O through the chipset.

TheRoosterneeb · ‎11-14-2018

Hey guys, I know this thread is probably extremely dead, but posting here for anyone else who stumbles upon this;

From the Motherboard manual .pdf on ASUS' website; https://www.asus.com/us/Motherboards/ROG-CROSSHAIR-VII-HERO/HelpDesk_Manual/

From page ix of the specifications summary, it says devices placed in M.2_2 will steal PCIE lanes from PCIE_SLOT_x8/x4_2.

Diagram of the .pdf's silkscreen, with the corresponding slots w/ respective colors.

You shouldn't see reduced performance as long as you're not running SLI/Crossfire on the board, or putting a graphics card in the x8 slot and running a M.2 SATA/NVME at the same time, for any people aspiring to run a dual NVME set-up like I will be. Honestly, this was a good move from ASUS, using the bandwidth second slot that most experienced PC builders wouldn't be using anyway, since it's an x8 lane to begin with. I'd say if you wanna go full cordless, use this lane for another PCIE storage device, or leave it empty, which is what I would so since it's too close to the x16 PCIE for adequate airflow for your GPU.

sdamico · ‎11-25-2018

TheRoosterneeb wrote:
Hey guys, I know this thread is probably extremely dead, but posting here for anyone else who stumbles upon this;

From the Motherboard manual .pdf on ASUS' website; https://www.asus.com/us/Motherboards/ROG-CROSSHAIR-VII-HERO/HelpDesk_Manual/

From page ix of the specifications summary, it says devices placed in M.2_2 will steal PCIE lanes from PCIE_SLOT_x8/x4_2.

Diagram of the .pdf's silkscreen, with the corresponding slots w/ respective colors.

You shouldn't see reduced performance as long as you're not running SLI/Crossfire on the board, or putting a graphics card in the x8 slot and running a M.2 SATA/NVME at the same time, for any people aspiring to run a dual NVME set-up like I will be. Honestly, this was a good move from ASUS, using the bandwidth second slot that most experienced PC builders wouldn't be using anyway, since it's an x8 lane to begin with. I'd say if you wanna go full cordless, use this lane for another PCIE storage device, or leave it empty, which is what I would so since it's too close to the x16 PCIE for adequate airflow for your GPU.

Yes, I've been confused by reviews and posts stating the M.2_2 was sharing lanes with the PCIE_1, which is not what the manual states. Hopefully the manual is correct, but either way I'm running dual M.2 Samsung EVO 970s.

theAlmightyEyeb · ‎09-26-2019

TheRoosterneeb wrote:
Hey guys, I know this thread is probably extremely dead, but posting here for anyone else who stumbles upon this;

From the Motherboard manual .pdf on ASUS' website; https://www.asus.com/us/Motherboards/ROG-CROSSHAIR-VII-HERO/HelpDesk_Manual/

From page ix of the specifications summary, it says devices placed in M.2_2 will steal PCIE lanes from PCIE_SLOT_x8/x4_2.

Diagram of the .pdf's silkscreen, with the corresponding slots w/ respective colors.

You shouldn't see reduced performance as long as you're not running SLI/Crossfire on the board, or putting a graphics card in the x8 slot and running a M.2 SATA/NVME at the same time, for any people aspiring to run a dual NVME set-up like I will be. Honestly, this was a good move from ASUS, using the bandwidth second slot that most experienced PC builders wouldn't be using anyway, since it's an x8 lane to begin with. I'd say if you wanna go full cordless, use this lane for another PCIE storage device, or leave it empty, which is what I would so since it's too close to the x16 PCIE for adequate airflow for your GPU.

I have two evo nvme 3x4 ssd drives and a vega64 in the x16 slot.
Every utility I used to check my GPU tells me it is running at x16.
The m2_2 slot does not reduce the first pci slot to x8.

Frankyvee · ‎07-15-2019

schweigert wrote:
wow..... thanks for this info. I was going nuts, figuring out why my card was only at 8x

now i wonder whats the net best config --- m.2 using pcie lanes w/ card at 8x. or m.2 using the bottom mount non pcie but card at 16x?

Install your M.2 drive in the bottom slot since it has a direct path to the CPU. The top slot is stealing PCIe lanes from the main x16 Graphics Slot and you probably won't notice it until you put some demand on our GPU like a high fps game.

Tex-Rec · ‎03-28-2019

brkkab123 wrote:
The top m.2 slot that has the heat-sink on it does use PCIe lanes.
If you use it your x16 PCIe slot will only use x8 speeds.
m.2 slot 2 on the bottom doesn't use PCIe.
If you have a single m.2 ssd use the lower m.2 slot for it.

I just noticed today , when walking a little bit trought the BIOS that my EVGA GTX 1080 FTW2 runs at 8x instead of 16 and im using a single m.2 on the bottom slot since i builded this rig. Now i wonder why , as i known this before and thought i run it like it should runn , but it sems something wrong. Bios is on the latest version 2008 and im on the ASUS RGO Crosshair Hero 7.

is there a solution to give the GPU back 16x , btw the GPU is pluged in the First slot ( right below the rams )

EDIT: Reseated the GPU seems to solve my problem , a little dust evil landed on a pin , cleaned with 100% Alkohol all the pins , pluged in and 16x was again active.

bigtop1967 · ‎03-29-2019

Tex-Rec wrote:
I just noticed today , when walking a little bit trought the BIOS that my EVGA GTX 1080 FTW2 runs at 8x instead of 16 and im using a single m.2 on the bottom slot since i builded this rig. Now i wonder why , as i known this before and thought i run it like it should runn , but it sems something wrong. Bios is on the latest version 2008 and im on the ASUS RGO Crosshair Hero 7.

is there a solution to give the GPU back 16x , btw the GPU is pluged in the First slot ( right below the rams )

Yes - this happened to me. In the bios you can force x16 and disable M.2_2:

In the bios go to - Advanced>OnboardDeviceConfiguration>M.2_2 PCIe Bandwidth Configuration

Choose [Disabled(X8 mode)]

This disables M2._2 and gives you X16 for your GFX and X4 for your M.2_1

Hope this helps

About me: I am dyslexic and DO occasionally miss things!

There are 10 types of people, those who understand binary, and those that don't.
F people in 10 don't understand hexadecimal

Crosshair VII: M.2 drives steal PCIE bandwidth