NVME M.2 sharing bandwidth with GPU in x16 slot 1?

[shen.matt92]

I have a Samsung NVMe 970 1TB in x4 PCIE mode on an Asus Z370 Prime-A. I also have a GTX 1080 TI FTW3 in PCIE 3.0x16_1.

When the NVME is installed, the GPU runs at x8 as seen in the BIOS. When I switched to a Samsung Evo 860 SATA M.2, it shows its at x16 speed.

My guess is, since the Hyper M.2 NVME was disabled and removed and replaced by the SATA M.2, they no longer share bandwidth since SATA is not PCIE but NVME is.

Weird thing is, on my mobo manual it clearly states when an NVME in M.2 socket 1 is used, SATA 5 and 6 are disabled, but makes no mention of affecting the GPU lane.

Another odd problem I'm having is witht he NVME when Windows boots and first goes to sign in and desktop, the resolution is 4:3, either 1024X768 or 1280X1024, forgot which one. Then when I change it to 3840X2160, everytime I reboot it always loads the 4:3 one and must be changed again. It has something to do with the Microsoft basic display adaptor overriding my GPU drivers. Tried reinstalling GPU, everything. Whats weird is this wasn't happening on my old mobo, which is the exact same one. Only started when I got the brand new Asus Prime. If it helps my old one was an open box. But Id imagine if one had problems itd be the open box one, not the new one. Even odder, when I change the M.2 to the SATA 860 Evo the problem goes away.

In the last 2 days Ive reinstalled windows probably 10 times just running these tests for comparison. For some reason my new mobo is behaving differently even though the settings are the same and the model and make is the same and they were only manufactured a few months apart.

Also noticed Evo 860 SATA with magician runs at 6000mbps but the NVMe only does 3500. But thought NVMe is supposed to be better.

I'm trying to hurry up and learn all this by the time the 2080 comes out because I have to decide whether I want to buy the card and set up a new PC myself or just say eff it and have Alienware or Origin do it.

Sorry to go off topic there, thought maybe some of you guys would have answers to both instead of making a new thread.

 

[bmockeg]

You aren't setting something right in the bios. M.2 NVME don't share bandwidth with x16 GPU pcie slots.

 

[Darkbreeze]

PCI M.2 will knock out SATA, not the other way around. Also, I agree with the above post that I've never seen an M.2 drive, whether SATA or PCI, take bandwidth from the x16 primary PCIe slot. Secondary slots, sure. Not the primary graphics lanes though.

First thing you should do is make sure you have the latest bios version installed. Generally, early bios releases have a lot of bugs that have to be worked out in later releases. I've never seen THAT particular one, but I guess anything is possible and I HAVE seen some peculiar M.2 related compatibility and support issues on early bios before, so I guess it's possible. It's more likely that it's a configuration problem somewhere in the bios or it might even be a faulty board.

Also, there's no possible way your 860 EVO runs at that speed. Maximum sequential speeds for that drive are 550/520mbps.

 

[shen.matt92]

Ive heard that they don't. But what makes me think it has to do with that is the fact I switched to the SATA m.2 and it all of a sudden appears as x16 when I didn't change anything else. Don't think that's a coincidence.

 

[Darkbreeze]

What do you mean "switched" to SATA M.2? Is your M.2 drive PCIe or SATA? Or do you have one of each? What is your motherboard model? Maybe you are trying to use the wrong kind of drive in a slot that wasn't meant for it. SATA and PCIe M.2 drives are not compatible with all slots. Some M.2 slots are only meant for one or the other, although some are capable of using either one. It fully depends on the board, and WHICH slot on the board if it has more than one, which many of them do.

 

[mdd1963]

there is a VERY big difference in 6000 Mbps (SATA 3 spec) and 3500 MegaBytes/sec...

 

[bmockeg]

Have you tried just using the lower m.2 slot?

 

[shen.matt92]

What do you mean "switched" to SATA M.2? Is your M.2 drive PCIe or SATA? Or do you have one of each? What is your motherboard model? Maybe you are trying to use the wrong kind of drive in a slot that wasn't meant for it. SATA and PCIe M.2 drives are not compatible with all slots. Some M.2 slots are only meant for one or the other, although some are capable of using either one. It fully depends on the board, and WHICH slot on the board if it has more than one, which many of them do.

Thanks for your reply man. I mean switched as in just turned off my computer, put the SATA m2 in the same slot the nvme was in, then installed windows after making the proper bios alterations. My mobo manual states that m2 slot 1 can be used for either nvme or sata, and in my bio settings m2 slot 1 can be changed from pcie mode or sata.


I understand all the keying as well, m+b being sata and having a maximum speed of x2, m key having x 4. I read up on all that to make sure everything was compatible.


But what weirds me out most is just how the nvme does fine on the old mobo even though its the same one. The reason I switched to a new asus prime was because I was experiencing frame drops in games, bought all my parts new except the mobo which was open box. Also, Ive had multiple power outages which caused me to think it may have damaged my mobo or ssd. So I was like what the heck ill buy new ones and see if it improves. turns out my gtx 1080 was only running at stock (1569mhz) and I used EVGA OC to increase it to 1930mhz which fixed most micro stuttering and fps drop. But then I happened to notice these other issues that came alive only with the new mobo.


Technically this isn't really a problem because I can just go back to my old mobo but I cant help but be curious as to why.

Here are some other details might help:

When installing the nvme on the new mobo I forgot to put the standoff screw and slightly flexed it.
had multiple power breaker trips (theres something wrong with my electricity in my apartment) and power shut off multiple times during playing games and downloading or installing windows

 

[shen.matt92]

there is a VERY big difference in 6000 Mbps (SATA 3 spec) and 3500 MegaBytes/sec...

yeah sorry I recently learned of the difference between megabits and megabytes but on Samsung magician 860 evo sata m2 has a read speed of 7000 MB/s on rapid mode but the nvme cant do rapid mode

 

[shen.matt92]

Have you tried just using the lower m.2 slot?

I have. m2 slot one is the lower one, furthest away from cpu.

 

[bmockeg]

Is there any difference between slots when you test performance?

 

[Darkbreeze]

One of those slots supports both SATA and PCIex4 while the other slot supports only PCIe. So either slot should work for a PCIe NVME M.2 drive, however I'd probably want to use whichever slot had the biggest lane allowance and I think that might be the one that does not support SATA since the specs say

*1. The M.2_1 socket shares SATA_1 port when use M.2 SATA mode device. Adjust BIOS settings to use a SATA device.
*2. The M.2_2 socket shares SATA_5/6 ports when use M.2 PCIE mode device in X4 mode. Adjust BIOS settings to use M.2 PCIE devices

So one of them only takes lanes from a single SATA header while the other one takes them from two of them. Seems that one would have more available lanes then. Also, be sure that you have enabled PCIe NVME M.2, specifically that, in the bios settings as the notes indicate.

As bmockeg has indicated, I'd try both slots. I'll say again as well, make sure you have the VERY latest bios installed, and that you've configured the settings for M.2 PCIe devices properly in the bios afterwards.

If none of this helps, then I'd say you need to contact ASUS regarding an RMA, or at least to see what they think is going on. Sometimes these manufacturers tech support isn't terribly helpful though.

 

[Peter Martin]

i thought you always wanted to use NVMe in Gen3x4 lanes, not x16, isn't that all they can handle anyway?

 

[Darkbreeze]

Yes. I do not believe there are any M.2 devices that natively run at x8 speeds. There are adapters for x8 slot use, but I do not think they will allow any NVME PCIe drive to go beyond it's spec. That would be silly. The 970 EVO series is of course x4, so there is no way it could be using x8 lanes. It must be a fault or a configuration problem.

Might even be related to demand for the graphics card. Sometimes monitoring software doesn't show graphics cards using x16 or PCIe 3.0 speeds until there is a need for it to do so. GPU-Z for example will often show a 3.0 card running at 2.0 until it is under a load.

 

[shen.matt92]

One of those slots supports both SATA and PCIex4 while the other slot supports only PCIe. So either slot should work for a PCIe NVME M.2 drive, however I'd probably want to use whichever slot had the biggest lane allowance and I think that might be the one that does not support SATA since the specs say

*1. The M.2_1 socket shares SATA_1 port when use M.2 SATA mode device. Adjust BIOS settings to use a SATA device.
*2. The M.2_2 socket shares SATA_5/6 ports when use M.2 PCIE mode device in X4 mode. Adjust BIOS settings to use M.2 PCIE devices

So one of them only takes lanes from a single SATA header while the other one takes them from two of them. Seems that one would have more available lanes then. Also, be sure that you have enabled PCIe NVME M.2, specifically that, in the bios settings as the notes indicate.

As bmockeg has indicated, I'd try both slots. I'll say again as well, make sure you have the VERY latest bios installed, and that you've configured the settings for M.2 PCIe devices properly in the bios afterwards.

If none of this helps, then I'd say you need to contact ASUS regarding an RMA, or at least to see what they think is going on. Sometimes these manufacturers tech support isn't terribly helpful though.

Yes the NVME has been enabled and the speed is at x4. Im very familiar with the layout of this motherboard since Ive been dealing with it for months. But this was my first build and I have no idea how to update the BIOS or anything like that. But I don't think that's necessary. Im thinking about taking pictures or screenshots of every single page in the new mobos BIOS and comparing it to that of the old one. Its just a huge pain in the ass switching parts all the time especially since my chassis is an Alienware triad area-51 I got off eBay. The case weighs like 50 pounds and I gotta lift it every time I make hardware swaps. Not to mention unplugging every cable and waiting 10-15 seconds to unplug the power supply after power down. At least I heard that's what must be done.

Ive looked up why the 860 has a speed of 6000MB/s with Samsung Magician and people say its an incorrect reading. But someone at my local computer store told me Samsung Magician uses your RAM as a buffer to greatly increase the speed. I even notice sometimes, it responds faster than the NVME, mostly with loading apps and Windows. When you click on an app, sometimes it will open instantly in the blink of an eye. But in games I don't see any difference.

I suppose if its true that Magician software greatly increases the speed of the 860 SATA m2 to 6000 MB/s, Id imagine there'd be instability and NVME is more stable. With BOTH NVME and SATA m2 sometimes when I click on Steam, even only once, it will say "not responding". And I have an 8700K with 16GB 3000MHz RAM in XMP. Also, NVME really isn't much more cost wise. My 860 Evo was $130 for 500GB and my Samsung 970 NVME is 1TB for $350. So that's only a $90 difference for 1TB.

 

[shen.matt92]

Something extremely important I forgot to mention...

Not only does the GPU show up as running at x8 when the NVME is installed, but it also shows up as PCIE 3.0_2, meaning second slot. But when SATA M2 is installed, its PCIE 3.0_1 in BIOS.

So my observations are

1) When NVME is installed, GPU is at x8. When switched to SATA M2, its x16

2) When NVME is installed, GPU is PCIE 3.0x_2. When switched to SATA M2, its _1

3) SATA M2 is not PCIE 3.0 but NVME is, and GPU is PCIE 3.0. Yet the Mobo manual doesn't say it shares bandwidth with the GPU lane. And we can all agree on that. I even read that the first two lanes are controlled by the CPU chipset and the M2 is controlled by the Mobo chipset, Z370, and therefore can't share bandwidth with the GPU_1 lane. Yet all the evidence seems to support that it does.

Ill switch to my old mobo and report results later today.

 

[Peter Martin]

so apparently on your mobo, when you plug in that nvme drive, it bumps the GPU to an x8 slot... lol, sorry. looking into it. It's not sharing anything, it's kicking your gpu down a notch or so it seems

 

[Darkbreeze]

Which should not be possible. You need to contact ASUS. Personally, I think you need to try the bios update first. These days, BIOS updates affect EVERYTHING from CPU behavior, to memory compatibility, to support for graphics cards and right down to how the motherboard processes and distributes access to the PCI lanes. It could be bios related or it could be a bad board. Seems doubtful that it might be configuration, since what it's doing shouldn't even be possible.

 

[Darkbreeze]

On second thought, you might want to pull your CPU cooler and processor, and take a very close look at the motherboard pins using high powered reading glasses or a magnifying glass. If there is even ONE single pin out of alignment, or looks "off" from all the others, it's possible you might have bent a pin on the socket bed when installing the CPU. I've already found several other Z370 forum entries where the GPU card was reducing to x8 speeds when any other PCIe device was being used due to bent motherboard pins in the CPU socket.

 

[USAFRet]

yeah sorry I recently learned of the difference between megabits and megabytes but on Samsung magician 860 evo sata m2 has a read speed of 7000 MB/s on rapid mode but the nvme cant do rapid mode

RAPID mode does not count.
That "7000 MB/s" is mainly reading the speed of your RAM, not the drive.

That's how the RAPID mode works.
It uses a chunk of your actual RAM as a cache for the SSD.
And actually, it is mostly useless apart from showing you magic benchmark numbers.

Turn it OFF.

 

[Darkbreeze]

Exactly. Not realistic, doesn't actually speed up random access or sequential file transfers. I've verified that on many occasions. All my Samsung drives have it turned off. Just reserves RAM for basically no benefit.

 

[jumpinseth17]

Just made an account for this post. Not sure if I am posting correctly but here goes.

I have a maximus hero x wifi. 960 Pro in the bottom m.2 slot and a 860 evo in the top m.2 slot. All maximum bandwidth modes enabled for the m.2s. Running SLI 1080ti's with a 8700k. A 860 evo and a 840 evo sata drives, and a WD Black. SATA 1 and 6 are disabled due to having 2 m.2s. I was running into something of this sort as well.

Occasionally on startup my top slot 1080ti will be reduced to x2! Giving me reduced frame rates and a terrible game play experience. Restarting the computer puts the cards back into x8, which is normal for SLI and my frames are perfect.

Strange because I know the setup works. I was worried about my lanes as well, but 75% of the time it boots normally. Other times it does not.

I have been looking for a solution to this as it is a bit of a pain. Next time I drain my loop I will inspect the pins as someone stated above. Just thought I would share my experience as well.

 

[Darkbreeze]

Please start your own thread. Every person's situation is somewhat different and it is preferred to create a new thread for each unique issue. Plus, you are far more likely to get help with a new thread than posting in an existing one.

 

[jumpinseth17]

Please start your own thread. Every person's situation is somewhat different and it is preferred to create a new thread for each unique issue. Plus, you are far more likely to get help with a new thread than posting in an existing one.

Sorry dark should I remove previous comment?

 

[USAFRet]

Please start your own thread. Every person's situation is somewhat different and it is preferred to create a new thread for each unique issue. Plus, you are far more likely to get help with a new thread than posting in an existing one.

Sorry dark should I remove previous comment?

Just create a new thread for your specific issue.