Crosshair VII: M.2 drives steal PCIE bandwidth

[donalgodon]

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.

[theAlmightyEyeb]

I installed two EVO Pro nvme drives on my Crosshair VII and everything was working like it should. Read and write speeds were at spec, they were using x4 lanes.
The only problem is: my GPU was still running at x16, which isn't really a problem if the info is correct, but from what I understand it is not supposed to do that.
I reset the BIOS, installed the nvme drives in a raid and stand alone arrays. All firmware was up to date with the latest 2304 BIOS, reloaded windows a couple of times...
Any diagnostic software I ran showed the GPU at 16x.
I ended up taking the second one out because it was making my system run really choppy at times.
Can someone explain this?

[xeizo]

theAlmightyEyeball wrote:
I installed two EVO Pro nvme drives on my Crosshair VII and everything was working like it should. Read and write speeds were at spec, they were using x4 lanes.
The only problem is: my GPU was still running at x16, which isn't really a problem if the info is correct, but from what I understand it is not supposed to do that.
I reset the BIOS, installed the nvme drives in a raid and stand alone arrays. All firmware was up to date with the latest 2304 BIOS, reloaded windows a couple of times...
Any diagnostic software I ran showed the GPU at 16x.
I ended up taking the second one out because it was making my system run really choppy at times.
Can someone explain this?

That is a bug, I don't remember exactly what it was but it is reporting wrong speed. With two M.2-drives the Graphics speed IS 8x.

Not that it matters much for the time being, my box with 2700X/1080Ti still gets better Firestrike Extreme score than 3900X/RTX 2080 and I run two M.2-drives, apparently 8x isn't restraining the 1080Ti much if at all. I dual boot two systems with different functionality(One game drive and one DAW drive).

Maybe with Nvidia Ampere on 7nm 8x will be a limitation, but not for the moment.

[gupsterg]

The video gorpo linked is correct, also the information posted by TheRoosterneeb is correct. Below is block diagram for ASUS ROG Crosshair VII Hero.

[Kamui004]

gupsterg wrote:
The video gorpo linked is correct, also the information posted by TheRoosterneeb is correct. Below is block diagram for ASUS ROG Crosshair VII Hero.

Yes, that's how the PCI-E Lanes are diagramed. But row 3 in the chart on page 1-8 of the manual illustrates how the PCI lanes are managed depending on what devices you have installed.
Basically putting a NVME ssd in the M2_2 is using part of the bandwidth from PCIEX8/X4_2, basically like you putting a second video card. Thus lowering to x8/x8 or in this case the motherboard will split the lanes down to x8/x4/x4.
So basically if you have 1 ssd and it's NVME put it in the M.2_1 slot, the lower one. If you put it on the upper M.2_2 your GPU on PICEX16 will work x8.

[gupsterg]

Kamui004 wrote:
Yes, that's how the PCI-E Lanes are diagramed. But row 3 in the chart on page 1-8 of the manual illustrates how the PCI lanes are managed depending on what devices you have installed.
Basically putting a NVME ssd in the M2_2 is using part of the bandwidth from PCIEX8/X4_2, basically like you putting a second video card. Thus lowering to x8/x8 or in this case the motherboard will split the lanes down to x8/x4/x4.
So basically if you have 1 ssd and it's NVME put it in the M.2_1 slot, the lower one. If you put it on the upper M.2_2 your GPU on PICEX16 will work x8.

I never disputed placing a NVMe in M2_2 does not take PCI-E lanes, nor did gorpo's info or TheRoosterneeb's.

[bigtop1967]

When you have a 3xxx CPU and pcie 4.0 GPU, it should be ok, as running it at 4.0 x8 will be the same as running it on ver 3.0 x16...

All of a sudden I'm kinda wanting a new pcie 4.0 NVMe and GPU - my new CPU isn't even here yet!

[xeizo]

bigtop1967 wrote:
When you have a 3xxx CPU and pcie 4.0 GPU, it should be ok, as running it at 4.0 x8 will be the same as running it on ver 3.0 x16...

All of a sudden I'm kinda wanting a new pcie 4.0 NVMe and GPU - my new CPU isn't even here yet!

Only that CH7 doesn't support PCIE 4.0 on the graphics slot, according to the Asus validation sheet which was leaked. Only on the M.2.

TuF and Prime supports PCIE 4.0 graphics.

So bottom M.2 it is, if you want max PCIE graphics performance.

I run two M.2 for now, as I can't think of anything that demanding in graphics I do which needs more than PCIE 3.0 8x. If anything that heavy appears, I will just have to move my main stick to the bottom M.2 and empty the top one.

But, AMD wants to prohibit use of PCIE 4.0 on anything but X570. I wonder for how long we will have this feature. Not for very long I'm afraid.

[IrshaadH]

Hey, so just to clarify this. If I run a single graphics card in the top slot and an m.2 NVME drive in the upper slot as well, the GPU will still run at x16?

Also, if I run an m.2 SATA drive, will that take up PCI lanes?

Thanks

[Oldar]

IrshaadH wrote:
Hey, so just to clarify this. If I run a single graphics card in the top slot and an m.2 NVME drive in the upper slot as well, the GPU will still run at x16?

Also, if I run an m.2 SATA drive, will that take up PCI lanes?

Thanks

Yeah, I have the same question as you! Can someone answer this as I want to buy an m.2 ssd BUT at the same time I already use all the 6 sata connections with other hdds.

[Frostie36]

There's no issue running a gpu at x8, that's what my 1080ti is running at as I'm using 2 pci-e cards so my gpu reduced from 16x to 8x but I have no issue in any games I play.

Steve over at gamers nexus did a youtube video a while ago testing gpu performance, comparing 16x vs 8x and the difference was just a frame or two at most in some games, the rest of the games he tested showed no difference at all & I believe he used a 2080ti.