Will 2x M.2 Nvme limit my GPU?

[Mazaih]

Hi everyone,

 

I'm building a new gaming PC, coming from an ancient HDD-based setup. I will be putting together following setup: Core i5-9600k on Asus Rog Strix 390-F (https://www.asus.com/Motherboards/ROG-STRIX-Z390-F-GAMING/specifications/) and GTX 1080Ti. I'm planning to have 2x M.2 Nvme PCIe SSD's for the system, one for the OS and one for games etc. Now reading about the Pcie SSD's i've suddenly become aware that having two in the system might drop the 16x PCIe for my GPU to 8x or even 4x? 

 

Could someone please help me to understand whether this is the case here or am I just misunderstanding something? Seems to be much more complicated than the traditional "plug cable in and play"

 

 

[H20Burner]

22 minutes ago, Mazaih said:

Hi everyone,

 

I'm building a new gaming PC, coming from an ancient HDD-based setup. I will be putting together following setup: Core i5-9600k on Asus Rog Strix 390-F (https://www.asus.com/Motherboards/ROG-STRIX-Z390-F-GAMING/specifications/) and GTX 1080Ti. I'm planning to have 2x M.2 Nvme PCIe SSD's for the system, one for the OS and one for games etc. Now reading about the Pcie SSD's i've suddenly become aware that having two in the system might drop the 16x PCIe for my GPU to 8x or even 4x? 

 

Could someone please help me to understand whether this is the case here or am I just misunderstanding something? Seems to be much more complicated than the traditional "plug cable in and play"

 

 

M.2s usually pull lanes from the pch. If it drops, there isn't too much performance loss in dropping from 16x to 8x hence why sli is still viable on the 16x lane cpus.

[Arttu89]

The short answer in your case is, yes it will dorp down the number of PCIe lanes for the GPU.

 

The long answer is, it depends.

 

A CPU has a limited number of PCIe lanes coming out of it and those lanes are sometimes, but not always, shared between diffrent PCIe devices in your computer (depending on how the motherboard is electrically wired and the number of available lanes from the CPU).

 

In your case:

- the i5-9600k has only 16 PCIe lanes coming out of it + the DMI 3.0 interface going out to the chipset (which is like another 4 PCIe lines, but operated by the chipset and shared between things like USB ports, SATA drives, NVMe M.2 ports if any are wired through the chipset, etc.)

- from what I can see in the manual for the motherboard you chose, one of the M.2 slots is wired through the chipset and the other is wired to the CPU

 

So yes, one of the drives will be taking away 4 of the lanes coming out of the CPU and your main PCIe slot will go down to 8x, however with a GTX 1080 Ti 8x on PCIe 3.0 is still enough to not cause any issues.

 

Even if you went with the 9700k you'd still run into the same "problem", to get more lanes you have to go into Ryzen or HEDT platforms - but you don't have to do it for the system you're building.  You don't need more with what you're building.

[Fasauceome]

3 minutes ago, Arttu89 said:

The short answer in your case is, yes it will dorp down the number of PCIe lanes for the GPU.

 

The long answer is, it depends.

 

A CPU has a limited number of PCIe lanes coming out of it and those lanes are sometimes, but not always, shared between diffrent PCIe devices in your computer (depending on how the motherboard is electrically wired and the number of available lanes from the CPU).

 

In your case:

- the i5-9600k has only 16 PCIe lanes coming out of it + the DMI 3.0 interface going out to the chipset (which is like another 4 PCIe lines, but operated by the chipset and shared between things like USB ports, SATA drives, NVMe M.2 ports if any are wired through the chipset, etc.)

- from what I can see in the manual for the motherboard you chose, one of the M.2 slots is wired through the chipset and the other is wired to the CPU

 

So yes, one of the drives will be taking away 4 of the lanes coming out of the CPU and your main PCIe slot will go down to 8x, however with a GTX 1080 Ti 8x on PCIe 3.0 is still enough to not cause any issues.

 

Even if you went with the 9700k you'd still run into the same "problem", to get more lanes you have to go into Ryzen or HEDT platforms - but don't do it for the system you're building.  You don't need more with what you're building.

This whole post forgets about chipset lanes

[Arttu89]

1 minute ago, fasauceome said:

This whole post forgets about chipset lanes

DMI 3.0 is the chipset lanes.

[Fasauceome]

4 minutes ago, Arttu89 said:

DMI 3.0 is the chipset lanes.

Sorry, what I had meant to say was that the Z390 chipset will always be supplying the m.2 bandwidth via chipset, until you use too many. There are also some funny rules about "disabling SATA ports" that I experimented with and found that they still work.

[CharminUltraStrong]

44 minutes ago, Mazaih said:

Hi everyone,

 

I'm building a new gaming PC, coming from an ancient HDD-based setup. I will be putting together following setup: Core i5-9600k on Asus Rog Strix 390-F (https://www.asus.com/Motherboards/ROG-STRIX-Z390-F-GAMING/specifications/) and GTX 1080Ti. I'm planning to have 2x M.2 Nvme PCIe SSD's for the system, one for the OS and one for games etc. Now reading about the Pcie SSD's i've suddenly become aware that having two in the system might drop the 16x PCIe for my GPU to 8x or even 4x? 

 

Could someone please help me to understand whether this is the case here or am I just misunderstanding something? Seems to be much more complicated than the traditional "plug cable in and play"

 

 

I have a similar system. I'm running 2x Adata SX8200 M.2 NVME drives with an i5 9600k on an MSI MPG GAMING PRO CARBON z390 and I notice no performance drops when compared to other 1070 FTW2's.

[Arttu89]

21 minutes ago, fasauceome said:

Sorry, what I had meant to say was that the Z390 chipset will always be supplying the m.2 bandwidth via chipset, until you use too many. There are also some funny rules about "disabling SATA ports" that I experimented with and found that they still work.

It still depends on how it's actually wired on a given motherboard, it should usually be described in the manual, what and when will get disabled.

 

i.e. the manual for the motherboard he chose (Asus Strix Z390-F) states that SATA6G_2 will get disabled, but only if he uses the M.2 port running through the chipset in SATA mode, so in theory if the M.2 runs in NVMe mode, that SATA port should still be active.

[Fasauceome]

9 minutes ago, Arttu89 said:

It still depends on how it's actually wired on a given motherboard, it should usually be described in the manual, what and when will get disabled.

 

i.e. the manual for the motherboard he chose (Asus Strix Z390-F) states that SATA6G_2 will get disabled, but only if he uses the M.2 port running through the chipset in SATA mode, so in theory if the M.2 runs in NVMe mode, that SATA port should still be active.

They cheat a bit on these, not sure why they aren't more clear.

[Mazaih]

Thanks for all the replies, it’s much appreciated!

 

So I would be better off using only one (1x) of the Nvme M.2 slots for ssd / as OS disk - then “normal” SATA ssd’s for all the rest?