Question Does running 2 M.2 nvme SSD effects my GPU performance with this motherboard?

[TheUnknownSources]

Hi guys. So I'm planning to get a ASUS ROG Strix X470, which has 2 M.2 PCIe slots, without getting a 2.5 SSD, will it effects my GPU performance?

 

[velocityg4]

No, the first two PCIe x16 slots are wired directly to the CPU (PCIeX16_1 and 2). If only one slot is occupied it work in x16 mode if two are occupied they work in x8 mode.

The primary M.2 slot has a dedicated x4 lanes to the CPU.

The x470 chipset has another x4 dedicated lanes to the CPU. This is shared among the second M.2 slot, USB ports, SATA, Networking and all other PCIe x1 and x16 slots. If the secondary M.2 slot is populated with an NVMe SSD you can no longer use PCIe slots 1_1 and 1_3. Which are the first two PCIe x1 slots. Also PCIeX16_3 switches to x2 mode.

What may be confusing you is NVMe RAID. Which requires the use of the Hyper M.2 x16 card. Which uses one of the the CPU dedicated PCIeX16 slots.

 

[TheUnknownSources]

No, the first two PCIe x16 slots are wired directly to the CPU (PCIeX16_1 and 2). If only one slot is occupied it work in x16 mode if two are occupied they work in x8 mode.

The primary M.2 slot has a dedicated x4 lanes to the CPU.

The x470 chipset has another x4 dedicated lanes to the CPU. This is shared among the second M.2 slot, USB ports, SATA, Networking and all other PCIe x1 and x16 slots. If the secondary M.2 slot is populated with an NVMe SSD you can no longer use PCIe slots 1_1 and 1_3. Which are the first two PCIe x1 slots. Also PCIeX16_3 switches to x2 mode.

What may be confusing you is NVMe RAID. Which requires the use of the Hyper M.2 x16 card. Which uses one of the the CPU dedicated PCIeX16 slots.

What about the ASUS ROG Strix B450-I Gaming Motherboard (Mini ITX) since it has only 1 PCIeX16, and as product manual states:

AMD Ryzen™ 2nd Generation / Ryzen™ 1st Generation Processors

• 1 x M.2_1 Socket 3 with M Key, type 2242 / 2260 / 2280 (PCIE 3.0 x4 and SATA modes) storage devices support
• 1 x M.2_2 Socket 3 with M Key, type 2242 / 2260 / 2280 (PCIE 3.0 x4 mode) storage devices support*

and M.2_2 slot doesn't support SATA.

 

[velocityg4]

What about the ASUS ROG Strix B450-I Gaming Motherboard (Mini ITX) since it has only 1 PCIeX16, and as product manual states:

AMD Ryzen™ 2nd Generation / Ryzen™ 1st Generation Processors

• 1 x M.2_1 Socket 3 with M Key, type 2242 / 2260 / 2280 (PCIE 3.0 x4 and SATA modes) storage devices support
• 1 x M.2_2 Socket 3 with M Key, type 2242 / 2260 / 2280 (PCIE 3.0 x4 mode) storage devices support*

and M.2_2 slot doesn't support SATA.

Yes, they did their own custom wiring. While it isn't the norm for B450. The second M.2 slot shares lanes with the PCIe x16. When M.2_2 is populated PCIe x16 will run at x8.

Look at the notes on the specifications page for ASUS motherboards.

｜｜ASUS USA

www.asus.com

 

[Raraku]

No, the first two PCIe x16 slots are wired directly to the CPU (PCIeX16_1 and 2). If only one slot is occupied it work in x16 mode if two are occupied they work in x8 mode.

The primary M.2 slot has a dedicated x4 lanes to the CPU.

The x470 chipset has another x4 dedicated lanes to the CPU. This is shared among the second M.2 slot, USB ports, SATA, Networking and all other PCIe x1 and x16 slots. If the secondary M.2 slot is populated with an NVMe SSD you can no longer use PCIe slots 1_1 and 1_3. Which are the first two PCIe x1 slots. Also PCIeX16_3 switches to x2 mode.

What may be confusing you is NVMe RAID. Which requires the use of the Hyper M.2 x16 card. Which uses one of the the CPU dedicated PCIeX16 slots.

I doubt I'm as knowledgeable as you in general but I'm confused by your answer because I was investigating this same (and other boards) very recently.

From what I determined, there is no Ryzen mobo currently that supports two M.2 installed without having some effect on GPU performance. I believe if a 2nd M.2 NVME is installed in the second slot, it switches the PCIe x16 lane to a x8 lane, which with some powerful cards (1080ti, 2080, 2080ti) can affect your GPU performance, though generally by a small amount.

 

[TJ Hooker]

From what I determined, there is no Ryzen mobo currently that supports two M.2 installed without having some effect on GPU performance. I believe if a 2nd M.2 NVME is installed in the second slot, it switches the PCIe x16 lane to a x8 lane, which with some powerful cards (1080ti, 2080, 2080ti) can affect your GPU performance, though generally by a small amount.

This is true of any Ryzen mobo that can run two M.2 SSDs at PCIe 3.0 x4. Most Ryzen mobos that have two M.2 slots will run the 2nd slot through the chipset at PCIe 2.0 x4 or PCIe 3.0 x2 (which are equivalent in terms of bandwidth), and the primary PCIe x16 slot bandwidth is not affected.

 

[Raraku]

This is true of any Ryzen mobo that can run two M.2 SSDs at PCIe 3.0 x4. Most Ryzen mobos that have two M.2 slots will run the 2nd slot through the chipset at PCIe 2.0 x4 or PCIe 3.0 x2 (which are equivalent in terms of bandwidth), and the primary PCIe x16 slot bandwidth is not affected.

Hi TJ, you're the same gentleman that helped me the other day.

I don't want to hijack op's thread, but I want to make sure I'm understanding you correctly.

Is it possible to find a Ryzen mobo (itx) that will support two M.2 NVME (with one being x4 and the other being x2, or whatever else) without changing my x16 PCIe lane to x8?

 

[TJ Hooker]

Ah yes, I remember your thread.

Yes, it is absolutely possible. If fact, the majority of boards I've seen would let you do this. The caveat being that the 2nd NVMe drive would operate at half its max theoretical bandwidth. I'm sorry if I didn't make that clear in your other thread.

 

[Raraku]

Ah yes, I remember your thread.

Yes, it is absolutely possible. If fact, the majority of boards I've seen would let you do this. The caveat being that the 2nd NVMe drive would operate at half its max theoretical bandwidth. I'm sorry if I didn't make that clear in your other thread.

That's no problem my friend. I'm not sure why I was under the impression that it was not possible - I was convinced that going AMD with my 2 NVMEs would result in x8 GPU performance. In fact I thought it said that clearly on the Asus page, but it could be I'm mistaken because I'm a bit of a noob.

If I put the first NVME in slot 1 (Samsung 970 EVO), and the slower in slot 2 (Intel 660P), might the Intel not be affected at all because its speeds are approximately half the Samsung?

 

[TJ Hooker]

What motherboard and CPU do you have?

 

[Raraku]

What motherboard and CPU do you have?

Actually I don't have any yet, but I'm planning a build soon. If you could help recommend a decent board that would accompany a 2600X and would allow me to run two M.2 NVME without hindering the x16 lane, I would give AMD strong consideration over Intel.

 

[TJ Hooker]

Every motherboard will list in their specs page whether an M.2 slot shares bandwidth with the PCIe x16 slot (usually denoted with a footnote). Just avoid any that say they do for either M.2 slot.