Two M.2 PCIE SSDs in a B450 Motherboard

[skink]

Hello everyone,

I am thinking about buying a WD Black SN750 M.2 SSD. I already own a WD Blue SSD. My motherboard, The Aorus B450 Pro (link here), has two M.2 slots. If I have two PCIE M.2 SSDs in my motherboard, what kind of effects will happen? So far, I've read in my motherboards manual that certain SATA ports will not be functional. I am okay with this because I have no hard drives that will need Sata ports. However, I have read other forums that say that your graphics card could possibly be impacted, or one of the SSDs would not perform as well as they are supposed to. Could anyone validate this information? Is it worth it to get two M.2s? Just for reference, I sent a picture of my motherboards manual.

 

Thanks

[Cyracus]

Second nvme drive (M2B) will run at pcie3x2. M2A may run at sata, pcie3x2 or pcie3x4.
Personally I'd put my OS drive in M2B (lower slot) because there will be negligible impact on performance from the lower speed.
The reason the second m.2 is limited is there's only so many pcie lanes to connect to the mobo, 24 iirc, there's 16 to the gpu, and 4 to first m.2, the chipset needs to communicate to the cpu over those lanes too, but it takes less than 2 lanes worth, so the there's the 2 you can give to the second m.2 (hope that makes sense)

[Grabhanem]

1 minute ago, Cyracus said:

Second nvme drive (M2B) will run at pcie3x2. M2A may run at sata, pcie3x2 or pcie3x4.
Personally I'd put my OS drive in M2B (lower slot) because there will be negligible impact on performance from the lower speed.
The reason the second m.2 is limited is there's only so many pcie lanes to connect to the mobo, 24 iirc, there's 16 to the gpu, and 4 to first m.2, the chipset needs to communicate to the cpu over those lanes too, but it takes less than 2 lanes worth, so the there's the 2 you can give to the second m.2 (hope that makes sense)

Something to add is that the chipset basically acts as a PCIe hub, so while everything on it shares the same PCIe 3.0 x4 of bandwidth, it can distribute it based on need, so usually you won't see any performance bottlenecking from that unless you're pegging both the SSD and say a 10gig network card at the same time.

[skink]

12 minutes ago, Cyracus said:

Second nvme drive (M2B) will run at pcie3x2. M2A may run at sata, pcie3x2 or pcie3x4.
Personally I'd put my OS drive in M2B (lower slot) because there will be negligible impact on performance from the lower speed.
The reason the second m.2 is limited is there's only so many pcie lanes to connect to the mobo, 24 iirc, there's 16 to the gpu, and 4 to first m.2, the chipset needs to communicate to the cpu over those lanes too, but it takes less than 2 lanes worth, so the there's the 2 you can give to the second m.2 (hope that makes sense)

I thought that M2B would be the one getting the lower performance. Also I have a SATA M.2, not NVME. Would that change anything?

[skink]

16 minutes ago, Grabhanem said:

Something to add is that the chipset basically acts as a PCIe hub, so while everything on it shares the same PCIe 3.0 x4 of bandwidth, it can distribute it based on need, so usually you won't see any performance bottlenecking from that unless you're pegging both the SSD and say a 10gig network card at the same time.

Okay, that sounds good. Thanks for the help

[Cyracus]

23 minutes ago, skink said:

I thought that M2B would be the one getting the lower performance. Also I have a SATA M.2, not NVME. Would that change anything?

A sata drive will not function in slot M2B.

[skink]

On 12/3/2020 at 9:07 PM, Cyracus said:

A sata drive will not function in slot M2B.

I'm pretty sure it will... look at my picture of the manual. It says that slot M2B only supports PCIE SSDs.