Question Will I get "full speed" from 2nd M.2 drive?

[greigm78]

I currently have a MSI B450M Mortar motherboard and have 1 x M.2 NVMe (WD Blue SN500) 250 GB drive in the primary M.2 slot.
I have a GTX 1070 in the primary PCI-e slot and just 1 x SATA SSD and 1 x SATA HDD.

I want to replace the SATA SSD with a second M.2 (another WD Blue SN500), but have read that some boards share bandwidth with PCIe lanes. Will the Mortar board give me such limitation if I opted for this set-up?

Cheers

 

[retroforlife]

PCI_E4 slot will be unavailable when an M.2 SSD is installed in the M2_2 slot. what manual says 🤔

 

[greigm78]

Think that is empty anyway. So possiby not affect me?

 

[retroforlife]

https://www.msi.com/Motherboard/support/B450M-MORTAR#down-manual

 

[retroforlife]

page 21

 

[retroforlife]

by the looks of that picture no it shouldnt

 

[retroforlife]

PCI_E4 is bottem slot

 

[Barty1884]

The M.2 slots will not eat away at PCIe lanes available to the GPU.
One M.2 is NVMe only, and uses the chipset PCIe lanes - but is Gen2 x4 (equilvant to Gen3 x2), so is not "full speed" for an NVMe x4 drive. The other is PCIe OR SATA drives, and is direct from the CPU.

AMD® B450 Chipset

• 4 x SATA 6Gb/s ports1
• 1 x M.2 slot (M2_2, Key M)1
  • Supports PCIe 2.0 x4 2242/ 2260 /2280 storage devices

AMD® CPU

• 1 x M.2 slot (M2_1, Key M)*1
  • Supports PCIe 3.0 x4 (AMD® Ryzen 1st and 2nd Generation/ Ryzen™ with Radeon™ Vega Graphics) or PCIe 3.0 x2 (AMD® Athlon™ with Radeon™ Vega Graphics)and SATA 6Gb/s 2242/ 2260 /2280 storage devices

https://www.msi.com/Motherboard/B450M-MORTAR/Specification

 

[greigm78]

The M.2 slots will not eat away at PCIe lanes available to the GPU.
One M.2 is NVMe only, and uses the chipset PCIe lanes. The other is PCIe OR SATA drives, and is direct from the CPU.


https://www.msi.com/Motherboard/B450M-MORTAR/Specification

So I won't get the full speed from the second M.2? Might as well keep the SATA drive if that's the case.

 

[Barty1884]

EDIT See popatim's response below. I had misread.

 

[greigm78]

Cool, thanks. Will consider alternative options.

 

[popatim]

M2_2 is PCIE2, not 3, so depending on which NVME drive you install you may see a performance impact when running benchmarks.

The performance difference between a Sata SSD and an NVME SSD is usually not noticeable by the user so you have plenty of options!

 

[greigm78]

Thanks. My main rationale is that I want to lose the SSD because it needs a SATA power cable. When replacing my PSU I had to install a second SATA power cable assembly just for that drive so had 2 other connectors just floating around, seems like a waste of space and untidy.
M.2 would solve that but not if it would lose performance too much.
I might go for the WD Black SN750 in the M.2_1 and move the SN500 to the M.2_2 slot. Run OS from the SN750 and games and shit from the SN500.
And clean up the cable discipline while I do so.

 

[Barty1884]

The argument for cable management is probably a poor driving factor in moving to another M.2 in all honesty.
I get where you're coming from, as additional SATA chains that are mostly wasted are a pain - but you're not going to see any gains in doing so, beyond cutting down on a SATA chain & a SATA cable from the motherboard.

If I were you, I'd relocate the 2.5" SSD to somewhere that it can run on the same chain as the HDD from the PSU.
While there may/may not be native mounts anywhere close, remember, SSDs have no moving parts & do not necessarily need to be 'secured'. If you don't move your system, or don't move it often, you could have it rest at the bottom of the case - or could invest in some velcro to secure it elsewhere.

Cuts down the additional SATA 'chain', but still needs the SATA data cable to the motherboard, of course.