If a board disables SATA3 ports when an M2 slot is used, will my drive speed be limited?

[zircon]

I'm looking into various Z370/390 boards and the Taichi for example says the following on PC Part Picker:
 

• The motherboard M.2 slot #1 shares bandwidth with SATA 6.0 Gb/s ports. When the M.2 slot is populated, two SATA 6.0 Gb/s ports are disabled.
• The motherboard M.2 slot #2 shares bandwidth with a SATA 6.0 Gb/s port. When the M.2 slot is populated, one SATA 6.0 Gb/s port is disabled.
• The motherboard M.2 slot #3 shares bandwidth with SATA 6.0 Gb/s ports. When the M.2 slot is populated, two SATA 6.0 Gb/s ports are disabled.

 

The motherboard spec says:

• *M2_1, SATA3_0 and SATA3_1 share lanes. If either one of them is in use, the others will be disabled.
• If M2_2 is occupied by a SATA-type M.2 device, SATA3_3 will be disabled.
• M2_3, SATA3_4 and SATA3_5 share lanes. If either one of them is in use, the others will be disabled

 

So based on this, if I'm using M2 NVME drives like 970 Evos, is my speed going to be limited in any way? SATA3 bandwidth is of course much slower than what the higher end Samsung drives are capable of. Even 2x SATA3 would not come close .

 

[WereCatf]

If you're asking will the speed of your NVME-drives be limited, then the answer is no. If you're asking if the SATA-ports' speeds will be limited, no, because those ports will be completely unusable, not just lower-speed.

[vanished]

My interpretation of this is there is no reduction in speed - it either works or it doesn't

[zircon]

I'm wondering about the NVME drive speed, not the SATA3 port speed, for clarity. So even though two of the M2 slots use 2x SATA3 ports and one of them uses 1x SATA3... there's no difference in speed between the three slots? I wouldn't have any problems using 3x 970 Evo/Pros for example?

 

Is there a way to figure out how many PCIE lanes this would use?

[Cereal5]

NVMe drives use either the PCIe bus or the SATA bus. Not both. Those that use the SATA bus, run on SATA speeds. Those that run on the PCIe bus usually run on 4 lanes. Speeds depend on the drive, but read speeds are usually around 30k mbps. Both the drive and the mobo have to be NVMe compatible to run on the PCIe bus.

[zircon]

I guess what I am ultimately trying to figure out is whether or not I can use 3 extremely fast drives on a particular board and enjoy maximum speeds with all three. (Edit: Along with a GPU and a PCIE SSD like an Optane 900p)

 

This review shows that the X470 Taichi for example has hamstrung speeds in one M2 slot, whereas the 370 version of the same board doesn't. But this info is nowhere in the board specs, or if it is, I can't find it.

 

https://www.techspot.com/review/1646-storage-performance-intel-z370-vs-amd-x470/

https://www.asrock.com/mb/AMD/X470 Taichi/index.asp#Specification

 

I would hate to buy a mobo only to learn of a speed limitation like this.

[Mira Yurizaki]

21 minutes ago, zircon said:

I guess what I am ultimately trying to figure out is whether or not I can use 3 extremely fast drives on a particular board and enjoy maximum speeds with all three. (Edit: Along with a GPU and a PCIE SSD like an Optane 900p)

 

This review shows that the X470 Taichi for example has hamstrung speeds in one M2 slot, whereas the 370 version of the same board doesn't. But this info is nowhere in the board specs, or if it is, I can't find it.

 

https://www.techspot.com/review/1646-storage-performance-intel-z370-vs-amd-x470/

https://www.asrock.com/mb/AMD/X470 Taichi/index.asp#Specification

 

I would hate to buy a mobo only to learn of a speed limitation like this.

As I understand it, Ryzen is capable of supporting only one NVMe drive at full speed directly. Everything else, including the PCIe slots not intended for graphics cards, goes through the chipset. For the motherboard linked in particular, adding another NVMe drive simply disables one of the PCIe slots.

 

As far as full performance goes, it depends on how many of those drives are banging away and to where. Intra-drive transfers are always going to be at full speed because the data is likely not going anywhere out. Inter-drive transfers may have a performance hit if it has to cross the chipset to CPU boundary, but it's likely not going to be that bad.

[KarathKasun]

In some systems SATA and PCIe-NVMe can use the same pins on the CPU or northbridge.  If NVME is inserted, the pins swap to PCIe functionality.

 

The slot with only one SATA port linked to it is likely 2x PCIe instead of 4x.