Does this exist?

[durillon]

ive been thinking, so you know how there is pcie to m.2 expansion cards like the ones sold by asus? is there an expansion card that has an m.2 interface (slots into an m.2 slot) yet has 2 extra m.2 slots on that card, effecitvely doubling the amount of m.2 slots? and if this were made, would it work?

[GOTSpectrum]

1 minute ago, durillon said:

ive been thinking, so you know there is pcie to m.2 expansion cards like the ones sold by asus? is there an expansion card that has an m.2 interface (slots into an m.2 slot) yet has 2 extra m.2 slots on that card, effecitvely doubling the amount of m.2 slots? and if this were made, would it work?

I mean, M.2 cards are just PCIe interfaces, if your setup has support for bifurcation I don't see why it wouldn't work. They would however run slower 

[mariushm]

The pci-e to 4 x m.2 works because 16 pci-e lanes are split into 4 x 4 lanes, using bifurcation, which must be supported in bios.

 

It's not guaranteed a single m.2 ( 4 pci-e lanes) can be further split, but if supported it's munch more likely to have 4 x1 slots and not  2  x2 slots.

 

If you mean 2 m.2 connectors both with 4 pci-e lanes, no, can't do that without an expensive switch chip.

[durillon]

2 minutes ago, mariushm said:

The pci-e to 4 x m.2 works because 16 pci-e lanes are split into 4 x 4 lanes, using bifurcation, which must be supported in bios.

 

It's not guaranteed a single m.2 ( 4 pci-e lanes) can be further split, but if supported it's munch more likely to have 4 x1 slots and not  2  x2 slots.

 

If you mean 2 m.2 connectors both with 4 pci-e lanes, no, can't do that without an expensive switch chip.

fair enough i guess, but would a 4x m.2 ssd still run at 1x speeds if you really wanted to sacrifice speed for capacity?

[Eigenvektor]

I'm not sure if m.2 bifurcation really would make sense, since there's hardly enough room for two NVMe's in that space.

 

There are PCIe cards that provide two m.2 slots, if the mainboard supports bifurcation.

 

10 minutes ago, durillon said:

fair enough i guess, but would a 4x m.2 ssd still run at 1x speeds if you really wanted to sacrifice speed for capacity?

In general, yes. Even a x16 GPU will run in a x1 slot, as long as it physically fits.

[PDifolco]

I think it doesn't exist because as M2 slots are located horizontally on the board it's physically not really feasible to extend it in any way ...

There's pcie adapters for that, or if you want really high capacity, SATA SSDs are way more convenient 

[QuantumSingularity]

I am also looking into these dual and quad (2-way and 4-way) M.2 to PCIe cards and one question is now raising - is a RAID configuration a must for the drives with the add-in card? What i want is to have my boot NVMe drive on my motherboard and in the 2nd PCIe 3 slot slide 4x 1TB NVMe drives with a card similar to this one. However will the drives be displayed as separate drives or it will be just one raid configuration?

I can get 1TB Kingston NV2 drives for less than €70 a piece which will be less than the cost of a single 2TB drive, which i'll split anyway into 2 volumes. So if i can have 4 separate drives in a single slot - sing me up immediately and i'm getting rid of the mechanical drives.

[mariushm]

The cards simply split the 16 pci-e lanes that exist in the pci-e slot, into 4 groups of 4 pci-e lanes, and with the support of BIOS (bifurcation) they're seen as 4 pci-e x4 slots, so you get 4 independent m.2 connectors.

No, you don't get RAID or anything like that, and it's actually NOT a good idea to use SSDs in RAID even if you could.

 

You have to pay attention to the number of actual pci-e lanes available in the slot. The slot may be physically x16 but electrically may have fewer lanes. 

Some motherboards will have two pci-e x16 slots for video cards, but the total number of pci-e lanes available for those slots is 16 so when you insert a card in the second slot, the first slot gets downgraded to  8 pci-e lanes and the second slot receives the other 8 pci-e lanes - you could probably still use one of those cards with 4 m.2 connectors in the second slot, but only 2 m.2 connectors would actually work, because the existing 8 pci-e lanes will be split into 2 groups of 4 pci-e lanes.

 

Other motherboards will have a physically x16 slot, but will have only 4 pci-e lanes going to it, or even worse... some motherboards only have 2 pci-e lanes.

Some motherboards will "share" the pci-e lanes with a 2nd or 3rd m.2 connector present on the motherboard;For example the slot may be x16 physically, may have 4 actual pci-e lanes in it, but if you actuallly use a nvme m.2 ssd in the 3rd m.2 connector on the motheboard, the bios may "take" 2 or 3 pci-e lanes and re-route them to the m.2 connector to get it working, and leave that pci-e x16 slot with only 1 or 2 pci-e lanes.

 

 

[QuantumSingularity]

Well, the mobo i'm currently using is B450 Steel Legend. Has 2 PCIe gen 3 x16 slots and when both are populated it says that PCIE1 runs in x16 mode PCIE4 in x4 mode. So i thought i'll put the 4 NVMe drives with the card in the first slot to use all the 16 lanes and relocate the poor old GTX 1070 to the 2nd slot in x4 mode. Shouldn't see any performance hit with a card this old.

 

Edit: Now just checked in the compatibility modes and looks like i might have to upgrade to B550 in order to use both M.2_1 and PCIE4 simultaneously, but i was thinking on doing that anyway once i get the 5800X3D  Thans for reminding me to check the modes when both slots AND the onboard m.2 are used.

[mariushm]

IF the bios supports bifurcation, then yes, you may be able to use such card to split the 16 pci-e lanes into 4 m.2 connectors.

 

On an average B450 motherboard that second pci-e x16 with 4 physical lanes will most likely have those pci-e lanes coming from the chipset, which means they're pci-e 2.0 lanes - so maximum 4 x 500 MB/s or 2 GB/s or equivalent to a pci-e 3.0 x2 slot.

 

Your board has according to https://www.asrock.com/mb/AMD/B450 Steel Legend/index.us.asp#Specification

 

2 x PCI Express 3.0 x16 Slots (PCIE1: x16 mode; PCIE4: x4 mode)*

*Supports NVMe SSD as boot disks
If M2_1 is occupied, PCIE4 will be disabled.

 

So they decided to actually route the 4 pci-e lanes from cpu that usually go to m.2 connector closest to cpu socket to both m.2 and that slot, and if you use a m.2 the slot is naturally unusable. On the upside, you get pci-e 3.0 lanes, so you'd get reasonable speed on the video card should you choose to use the slot with 4 lanes

 

Then this board also has 4 pci-e 2.0 x1 slots so you could use 4 pci-e x1 to m.2 adapters to get a nvme SSD working in each pci-e slot, but the speed will be limited to around 480MB-ish /s (because pci-e 2.0 x1 maximum bandwidth is 500 MB/s)

 

Also note

 

M2_2, SATA3_3 and SATA3_4 share lanes. If either one of them is in use, the others will be disabled.

 

 

 

 

[QuantumSingularity]

13 minutes ago, mariushm said:

IF the bios supports bifurcation, then yes, you may be able to use such card to split the 16 pci-e lanes into 4 m.2 connectors.

 

On an average B450 motherboard that second pci-e x16 with 4 physical lanes will most likely have those pci-e lanes coming from the chipset, which means they're pci-e 2.0 lanes - so maximum 4 x 500 MB/s or 2 GB/s or equivalent to a pci-e 3.0 x2 slot.

 

Your board has according to https://www.asrock.com/mb/AMD/B450 Steel Legend/index.us.asp#Specification

 

2 x PCI Express 3.0 x16 Slots (PCIE1: x16 mode; PCIE4: x4 mode)*

*Supports NVMe SSD as boot disks
If M2_1 is occupied, PCIE4 will be disabled.

 

So they decided to actually route the 4 pci-e lanes from cpu that usually go to m.2 connector closest to cpu socket to both m.2 and that slot, and if you use a m.2 the slot is naturally unusable. On the upside, you get pci-e 3.0 lanes, so you'd get reasonable speed on the video card should you choose to use the slot with 4 lanes

 

Then this board also has 4 pci-e 2.0 x1 slots so you could use 4 pci-e x1 to m.2 adapters to get a nvme SSD working in each pci-e slot, but the speed will be limited to around 480MB-ish /s (because pci-e 2.0 x1 maximum bandwidth is 500 MB/s)

 

Also note

 

M2_2, SATA3_3 and SATA3_4 share lanes. If either one of them is in use, the others will be disabled.

 

 

 

 

Yeah, saw that after i wrote the initial post. That's why i'll be going with the B550 Steel Legend and it should work.

 

AMD Ryzen series CPUs (Vermeer and Matisse)
- 2 x PCI Express x16 Slots (PCIE1: Gen4x16 mode; PCIE3: Gen3 x4 mode)*

*Supports NVMe SSD as boot disks

 

- 1 x Hyper M.2 Socket (M2_1), supports M Key type 2230/2242/2260/2280 M.2 PCI Express module up to Gen4x4 (64 Gb/s) (with Vermeer, Matisse) or Gen3x4 (32 Gb/s) (with Cezanne, Renoir and Picasso)**

 

Now i get what all the fuss was about around Ryzen's PCIe lanes and the B550 as a whole. Might as well get a Gen4 NVMe drive to slot in that Hyper M2_1 slot and retire my current gen3 one to the 2nd slot, getting rid of SATA completely.