Question Where should I install my M2 SSD?

[LS21]

I have a Z790 motherboard that drops the GPU slot to 8X if you install an M2 SSD in slot 1. From the manual, only PCIe 1 and M2-1 are connected to the CPU. The other slots are run from the chipset. I am installing a Gen 4 GPU and a Gen 4 nvme SSD. Is it better to install the SSD in M2 slot 2 (run from chipset vs CPU) and keep the GPU at 16X or install the SSD in slot 1 and keep it connected to the CPU even though this would drop the Gen 4 GPU to 8X?

 

[zinkles]

What are you planning on doing on the system?
Is storage bandwidth very important to you?
And what is your CPU? (include other specs as well)

The GPU running at PCIe 4.0 x8 is equal to it being put into a PCIe 3.0 x16 slot. you won't notice much of a difference unless you max out the GPU.

Same with the SSD. If its just for gaming, the SSD speed won't matter for performance. Either way, not as if your getting a substantial difference in speeds either.

 

[LS21]

Thanks for the response. Most demanding use will be games. CPU is Intel i7-14700k. Motherboard is MSI Tomahawk MAG Z790 Max. GPU is a rtx-4070 super. Running 32 GB of DDR5-6400 RAM.
Given these, would it make a difference where I put the Gen 4 SSD? I am not knowledgeable enough to know if losing the 8 lanes for the GPU is better or worse than running the SSD through the chipset vs the CPU. Would the answer be different if I was running a Gen 5 SSD?
Appreciate the help!

 

[boju]

14th gen has dedicated 16 pcie 4/5 lanes + 4 additional pcie 4 lanes (20 total) for m2. Pcie 5 m2 in first slot would halve pcie slot but pcie 4 m2 shouldn't, afaik.

Update bios just incase, 14th gen is newer than the board so manual explaining what'll happen is outdated.

 

[zinkles]

Thanks for the response. Most demanding use will be games. CPU is Intel i7-14700k. Motherboard is MSI Tomahawk MAG Z790 Max. GPU is a rtx-4070 super. Running 32 GB of DDR5-6400 RAM.
Given these, would it make a difference where I put the Gen 4 SSD? I am not knowledgeable enough to know if losing the 8 lanes for the GPU is better or worse than running the SSD through the chipset vs the CPU. Would the answer be different if I was running a Gen 5 SSD?
Appreciate the help!

You should be able to put the GPU and the SSD and have the GPU run at x16 speed, I think.

 

[LS21]

Thank you for your replies so far. It makes sense that the manuals did not keep up with the new CPUs. I have assembled my new PC and GPU-Z shows the GPU running at 8X. I have the GPU in PCIe 1 and the Gen 4 SSD in M2-1. I like that the CPU is capable of 20 lanes. Any ideas on how to get the GPU to use 16 of them?

 

[boju]

Assuming bios is on latest, change pcie gen to 4 from auto.

 

[LS21]

Bios is updated. I tried setting pcie to gen4 and m2 to Gen4 and pcie to x16 in various combinations. System will not boot in these configurations - defaults to bios menu . Had to put all back in auto to boot to Windows.

 

[boju]

Thanks @Aeacus his replies are non quoted, copy paste.

Does Windows need to be reinstalled after changing m2 pcie gen?

AFAIK: No. It's like changing HDD to SSD or SSD to NVMe. Doesn't matter.

I thought 14th gen Intel allowed m2_1 to be occupied with pcie 4 ssd while not compromising graphics card lanes?

CPU may allow it, but in the end of the day, it comes down to MoBo and how PCI-E lane access is configured.

Mobo specs clearly state;

4x M.2
M.2_1 Source (From CPU) supports up to PCIe 5.0 x4 , supports 22110/2280/2260 devices
M.2_2 Source (From Chipset) supports up to PCIe 4.0 x4 , supports 2280/2260 devices
M.2_3 Source (From Chipset) supports up to PCIe 4.0 x4 / SATA mode, supports 2280/2260/2242 devices
M.2_4 Source (From Chipset) supports up to PCIe 4.0 x4 , supports 2280/2260/2242 devices
8x SATA 6G
*PCI_E1 slot will be Gen5x8 when installing M.2 SSD in the M2_1 slot.
*SATA_1 & SATA_2 will be unavailable when installing M.2 SATA SSD in the M2_3 slot.

Specs: https://www.msi.com/Motherboard/MAG-Z790-TOMAHAWK-MAX-WIFI/Specification

Now, RTX 4070 Super is PCI-E 4.0 x16 GPU, while MoBo PCI_E1 slot is 5.0 x16. So even when MoBo sets the PCI_E1 slot to 5.0 x8, it is equal to 4.0 x16. So, nothing is lost when M.2 drive is in M.2_1 slot.

 

[boju]

Thought some more about this, we know now it's not possible to run pcie 16x with m2_1 occupied. Cpu can do it but not the motherboard. Pcie 5 8x would only be in account if graphics card was also pcie 5, so really your card would be running at 8x pcie 4. I think avoiding using top m2 slot would be the best thing to do. Nvme communicating directly to cpu or graphics card running 16x. Think the latter be more appealing. It's a shame can't have both.

 

[LS21]

Makes sense. Are there any Z790 motherboards that can take advantage of the Intel Gen 14 CPU’s 20 lanes and allow the Gen 4 GPU to run at 16x while the Gen 4 SSD runs?
My understanding is that AMD does not have these limits on PCIe but I was reluctant to get away from Intel after all these years.
Either way, it will likely not be noticeable for my use - just curious.

 

[boju]

Sorry im having trouble finding any. Maybe someone else has an idea.

 

[thestryker]

Makes sense. Are there any Z790 motherboards that can take advantage of the Intel Gen 14 CPU’s 20 lanes and allow the Gen 4 GPU to run at 16x while the Gen 4 SSD runs?
My understanding is that AMD does not have these limits on PCIe but I was reluctant to get away from Intel after all these years.
Either way, it will likely not be noticeable for my use - just curious.

I've honestly never seen a board before that didn't wire up the CPU lanes, but I guess I can't say that now. Seems MSI on their less expensive (sub $400) MAX refresh boards only wired up the shared PCIe 5.0 lanes (the non-MAX Tomahawk for example has CPU PCIe 4.0 lanes only).

There are plenty of motherboards that do not have this issue like the Asus TUF GAMING Z790-PRO WIFI (this model doesn't have WIFI 7) which should be in the same ballpark money wise. There are plenty of options available though so it shouldn't be hard to find though is something you would have to specifically look for.