NVMe gen 4 SSD in PCIe 2.0 16x slot

[Judeling]

Every generation of PCIe is twice as fast as the last. This means 16 lanes of PCIe 2.0 is equal to 8 lanes of 3.0 and 4 lanes of 4.0.

 

However, if I plug a 4.0 SSD into a 3.0 slot, it'll use just 4 lanes, cutting the bandwidth in half. And using a 2.0 slot would cut that in half again, leaving you with a fourth of the bandwidth.

 

My question is if there's a way to use all 16 lanes in a 2.0 slot. To adapt them to the 4 lane connector on the 4.0 SSD and get the full speed. Is there an adapter card I can use?

 

I would appreciate any help.

[Fasauceome]

theoretically this could be made possible, but I don't think a product like this exists, because the market segment for users of this product would be so narrow. Of all the PCIe x16 NVMe adapters I've seen, they all incorporate 4 separate NVMe slots instead of adapting one NVMe connection to a single 16x bus

Granted if this was real, I would be tempted to get one for myself

[RONOTHAN##]

Couple things:

1.) Basically all PCIe 2.0 motherboards I know don't support booting of PCIe storage, so unless you were going to use it as a spare storage, it wouldn't work.

2.) For the devices that have fully wired x16 slots of PCIe 2.0 (so basically Nehalem and older), you just aren't gonna saturate a full PCIe 4 x4 interface with data throughput in almost anything but benchmarks. 

3.) it would require PCIe switches, which are expensive, and you'll probably end up paying more than your system is worth for a drive and one of these adapters.

 

Basically, it's a very niche product that for 99% of situations makes no sense, so therefore it doesn't exist.

[Judeling]

51 minutes ago, RONOTHAN## said:

Couple things:

1.) Basically all PCIe 2.0 motherboards I know don't support booting of PCIe storage, so unless you were going to use it as a spare storage, it wouldn't work.

2.) For the devices that have fully wired x16 slots of PCIe 2.0 (so basically Nehalem and older), you just aren't gonna saturate a full PCIe 4 x4 interface with data throughput in almost anything but benchmarks. 

3.) it would require PCIe switches, which are expensive, and you'll probably end up paying more than your system is worth for a drive and one of these adapters.

 

Basically, it's a very niche product that for 99% of situations makes no sense, so therefore it doesn't exist.

I didn't know older motherboards couldn't boot off of PCIe storage. So I guess that definitely ruins my plans from the get go.

 

And it's too bad it's not as simple as merging pins somewhere on the card and using firmware and a driver to make it work somehow. I knew that would never work but I was hoping there was something out there.

 

Maybe it would actually make some sense to adapt a gen 4 ssd to 8 lanes of PCIe 3.0. Or even a card that supports two gen 4 SSDs on a 16 lane slot. But if it really is that expensive it just doesn't make any sense.

 

Thanks for your answer

[RONOTHAN##]

7 minutes ago, Judeling said:

I didn't know older motherboards couldn't boot off of PCIe storage. So I guess that definitely ruins my plans from the get go.

 

For the most part, unless you hack the BIOS of the board, if the board doesn't have an M.2 slot, it doesn't support NVMe boot. There are some exceptions to that, but as a general rule of thumb it's a pretty safe rule to follow. 

 

9 minutes ago, Judeling said:

Maybe it would actually make some sense to adapt a gen 4 ssd to 8 lanes of PCIe 3.0. Or even a card that supports two gen 4 SSDs on a 16 lane slot. But if it really is that expensive it just doesn't make any sense.

That's a little more likely to happen, since instead of needing 2 PCIe switches, you would only need one. That said, unless Direct Storage is actually a game changer (I still have my doubts) I wouldn't expect it to ever be made since outside of workstation/super heaver virtualization tasks, PCIe 4.0 SSDs don't really make sense, and even for those scenarios you want the top of the line hardware for the rest of the stuff before you want to be investing that heavily into your storage bandwidth. With Direct Storage, it actually has a shot of being useful because a lot of people still have Gen 3 systems, and for the most part you can just bifurcate the x16 link to your GPU and have 8 lanes to the SSD and 8 lanes to the GPU. It isn't a perfect solution, it's far from it, but it's a product that would make sense.

 

As for why I say it would be expensive, the Liqid Honey badger is basically the reverse of this concept, and it's solidly in "if you have to ask, you can't afford it" territory. The Gen 3 to get 4 version would probably be 1/4 the price, but 1/4 the price is still really expensive. 

[kokosnh]

6 hours ago, Judeling said:

My question is if there's a way to use all 16 lanes in a 2.0 slot. To adapt them to the 4 lane connector on the 4.0 SSD and get the full speed. Is there an adapter card I can use?

 

there is. And I'm even using it now, but with PCI-e 2.0 x8 bus (it's PCI-e 3.0 x8, but my CPU have only PCI-e 2.0), to adapt for 4 x PCIe 3.0 x4 SSD 

It's a PCI-e SWITCH (you may heard of it by PLX chip). I use the cheap PCI-e 3.0 x8 version on asmedia asm2824 https://pl.aliexpress.com/item/4000800378079.html, but you can buy a x16 version.  
It takes a PCI-e 3.0 x 8 from mobo (it's PCI-e 2.0 compatible) and make new 4 x 3.0 x4 PCI-e lanes  for the SSD 

The PCI-e 4.0 x16 switch cost more, then new MOBO + new CPU + new RAM -> so not very feasible solution, but well it's possible.

 

6 hours ago, RONOTHAN## said:

1.) Basically all PCIe 2.0 motherboards I know don't support booting of PCIe storage, so unless you were going to use it as a spare storage, it wouldn't work.

 

There are plenty PCIe 2.0 motherboard that support booting from PCIe, the problem is actualy booting NVMe, but you can still boot in PCIe legacy mode from SATAexpress drives (AHCI drives using PCIe interface), or SSD with legacy boot ROM, like Samsung 950 pro, or Plextor M8PeG (I use it). 
It just shows in the UEFI and you can boot to it. 

[Judeling]

4 hours ago, kokosnh said:

there is. And I'm even using it now, but with PCI-e 2.0 x8 bus (it's PCI-e 3.0 x8, but my CPU have only PCI-e 2.0), to adapt for 4 x PCIe 3.0 x4 SSD 

It's a PCI-e SWITCH (you may heard of it by PLX chip). I use the cheap PCI-e 3.0 x8 version on asmedia asm2824 https://pl.aliexpress.com/item/4000800378079.html, but you can buy a x16 version.  
It takes a PCI-e 3.0 x 8 from mobo (it's PCI-e 2.0 compatible) and make new 4 x 3.0 x4 PCI-e lanes  for the SSD 

The PCI-e 4.0 x16 switch cost more, then new MOBO + new CPU + new RAM -> so not very feasible solution, but well it's possible.

 

There are plenty PCIe 2.0 motherboard that support booting from PCIe, the problem is actualy booting NVMe, but you can still boot in PCIe legacy mode from SATAexpress drives (AHCI drives using PCIe interface), or SSD with legacy boot ROM, like Samsung 950 pro, or Plextor M8PeG (I use it). 
It just shows in the UEFI and you can boot to it. 

The card you're talking about takes 8 lanes and doubles them so you have 16 (4x4). But what I'm looking for is the exact opposite, which would take 16 lanes and combine them into just 4 lanes, quadrupling the speed of those 4 lanes. I don't think the adapter you're using would be able to do what I'm describing. At least not without heavy modification. It would have turn PCIe 2.0 x16 into PCIe 4.0 x4. Or maybe PCIe 3.0 x8 into PCIe 4.0 x4, since that seems to be more feasible.

 

I appreciate your perspective though

[kokosnh]

No, It's exactly that.  
The PCIe SWITCH creates new PCI-e lanes, so it doesn't matter how many it creates, just so you can use it (it doesn't matter that it creates 4 time more PCIe lanes that you need).
The important part is that the version of the interface that it communicates with motherboard is independent to the PCi-e lanes it creates.

So If you buy a PCI-e 4.0 x16 SWITCH, that creates 4 x PCI-e 4.0, and plug it to the PCI-e 2.0 x16 slot on motherboard. Than It will work with the PCI-e 2.0 x16 (6400MB/s) on motherboard side, but will still create new PCI-e 4.0 x4 lanes for the SSD (that all share that bus speed 6400MB/s). 


I do it With PCI-e 3.0 x8 SWITCH, so less extreme, but it work the same. 
I linked to my PCIe 3.0 x8 SWITCH, but You would need a PCIe 4.0 x16 SWITCH to get it working. And these cost like fortune. 
The Broadcom PEX 88000 switches are what you are looking for, but i can't find any commercially available ready product, found only a Broadcom PCIe 3.0 x 16 PCIe switches max. It's usually enterprise grade stuff so no surprise here.