What's the difference between an m.2 NVMe plugged into MOBO vs into PCIe slot?

[Ghgsrt]

Just want to know if there are any advantages/disadvantages with using one over the other and if it's worth buying something like the ASUS Hyper M.2 

 

Thanks!

[themctipers]

pcie to m.2 probably has like 1% overhead because ??? and maybe 1% higher latency (not enough for anyone to care at the consumer level)

 

use the m.2 port on your motherboard if it has it, and if it doesn't then you could get a pcie to m.2, but don't buy a NVMe M.2 card (probably wouldn't recognize it and unbootable)

[reniat]

i'm like 51% sure that m.2 slots on motherboards will use the chipset PCI-e lanes, while the m.2 extension cards use the CPU's PCI-e lanes. This isn't really a huge deal if you are only using a single GPU and no other expansion cards, as you have 16 slots from CPU (typically) and a gpu can work fine on 8 lanes of PCI 3.0. 

[Mira Yurizaki]

There's practically zero difference.

 

3 minutes ago, reniat said:

i'm like 51% sure that m.2 slots on motherboards will use the chipset PCI-e lanes, while the m.2 extension cards use the CPU's PCI-e lanes. This isn't really a huge deal if you are only using a single GPU and no other expansion cards, as you have 16 slots from CPU (typically) and a gpu can work fine on 8 lanes of PCI 3.0. 

Unless you're using an Intel X series board, NVMe uses the chipset's PCIe lanes.

[zMeul]

1 minute ago, themctipers said:

pcie to m.2 probably has like 1% overhead because ??? and maybe 1% higher latency (not enough for anyone to care at the consumer level)

 

use the m.2 port on your motherboard if it has it, and if it doesn't then you could get a pcie to m.2, but don't buy a NVMe M.2 card (probably wouldn't recognize it and unbootable)

 

1 minute ago, reniat said:

i'm like 51% sure that m.2 slots on motherboards will use the chipset PCI-e lanes, while the m.2 extension cards use the CPU's PCI-e lanes.

 

bullcrap on both accounts

 

1. there is no overhead, the m.2 PCIe cards have no additional chips, just Copper traces to the m.2 slot
2. m.2 / PCie cards use PCH lanes; and as far as I'm aware it's the same for AM4 platform

to the OP: the benefit of a PCie m.2 card could be moving the SSD away from the heat sources (GPU); there are solutions out there that have heatsinks for m.2 SSDs

[agent_x007]

Well, if you don't have M.2 port on MB you probably will use CPU lanes (because new-ish Intel chipsets like Z97 and older suck in PCI-e lane count).
Situation is reversed when CPU doesn't have PCI-e lanes at all (duh).

PS. You can make NVMe work in almost any motherboard with PCI-e and 64-bit support.
Because Clover and/or Duet software exists 

[themctipers]

Just now, zMeul said:

 

 

bullcrap on both accounts

 

1. there is no overhead, the m.2 PCIe cards have no additional chips, just Copper traces to the m.2 slot
2. m.2 / PCie cards use PCH lanes; and as far as I'm aware it's the same for AM4 platform

to the OP: the benefit of a PCie m.2 card could be moving the SSD away from the heat sources (GPU); there are solutions out there that have heatsinks for m.2 SSDs

in a perfect world..

 

jumping through more hoops on pcie will degrade performance by like 1MB because the cosmic gods don't feel happy today

it would have higher latency because its located physically farther away from the chipset than the m.2 slot, probably has slightly lower priority and it will have to be processed through the chipset (iirc m.2 is connected directly to the CPU.. I think.. probably wrong though, knowing intel's 16 lanes)

[NumLock21]

no difference

[knightslugger]

Just now, themctipers said:

it would have higher latency because its located physically farther away from the chipset than the m.2 slot

It's an academic argument at best.

[themctipers]

Just now, knightslugger said:

It's an academic argument at best.

?

[agent_x007]

5 minutes ago, themctipers said:

?

There is no way to distinguish between longer traces perf. drop, and for example sharing PCI-e speed lane perf. drop (which requires switching logic).

[Mira Yurizaki]

5 minutes ago, themctipers said:

jumping through more hoops on pcie will degrade performance by like 1MB because the cosmic gods don't feel happy today

• This can happen regardless of where the drive sits
• 1MB out of 2GB/s of performance lost? Oh noes

5 minutes ago, themctipers said:

it would have higher latency because its located physically farther away from the chipset than the m.2 slot, probably has slightly lower priority and it will have to be processed through the chipset (iirc m.2 is connected directly to the CPU.. I think.. probably wrong though, knowing intel's 16 lanes)

Unless the board is an Intel X-Series board, M.2 goes through the chipset.

 

(note where it says "Intel PCIe Storage Device" on the bottom right)

 

[agent_x007]

21 minutes ago, M.Yurizaki said:

Unless the board is an Intel X-Series board, M.2 goes through the chipset.
(note where it says "Intel PCIe Storage Device" on the bottom right)

That's why I use NVMe Samsung SM961 with my LGA 2011

[Mira Yurizaki]

Just now, agent_x007 said:

That's why I use NVMe with my LGA 2011

Except that it doesn't really matter. Will going through the chipset instead of the CPU directly add latency? Sure. Does it hamper performance in any appreciable way in most applications? No.

[agent_x007]

9 minutes ago, M.Yurizaki said:

Except that it doesn't really matter. Will going through the chipset instead of the CPU directly add latency? Sure. Does it hamper performance in any appreciable way in most applications? No.

In most Z170/Z270 based motherboards, using M.2 port will "kill" SATA ports ("kill" - ie. switch off).
So performance - no it won't hamper (if M.2 gets PCIe 3.0 x4 speed), but it will limit expandability you can get out of your motherboard.