M.2 A/E Key comes pre-bifurcated with TWO PCIe x1 lanes?

[rcmaehl]

Hi all,

 

I'd figure that I'd ask in this section as the mining community seems to have a good grasp on odd PCIe risers, adapters, etc.

 

Per the PCI-SIG m.2 NGFF specification. The A and E keys come Pre-Bifurcated with TWO PCIe x1 Lanes.

 

Source: Official PCI-SIG m.2 Specification Revision 1.0 Page 23

 

Oddly enough, I would think that adapters for m.2 A/E -> TWO PCIe x1 would be popular for the mining crowd since it's basically 2 additional PCIe slots from one m.2. Is there a reason this isn't the case?

[Zando_]

That's saying they use 2 lanes, not split them out for other devices. Same as home most NVMe SSDs use 4 lanes (Key M on that sheet), or GPUs typically use 16 or more rarely, 8 lanes. It's not bifurcation that is a completely different thing (the CPU or a dedicated chip splitting a slot into sets of lanes for multiple other devices to use).

[rcmaehl]

4 minutes ago, Zando_ said:

That's saying they use 2 lanes, not split them out for other devices. Same as home most NVMe SSDs use 4 lanes (Key M on that sheet), or GPUs typically use 16 or more rarely, 8 lanes. It's not bifurcation that is a completely different thing (the CPU or a dedicated chip splitting a slot into sets of lanes for multiple other devices to use).

Are you sure? Key B definitely uses 2 lanes, but it's indicated correctly by PCIe x2. This is specifically 2x PCIe x1. 

[Zando_]

7 minutes ago, rcmaehl said:

Are you sure? Key B definitely uses 2 lanes, but it's indicated correctly by PCIe x2. This is specifically 2x PCIe x1. 

It looks like a weird way of stating it, I can't find any adapter that splits M.2 Key A/E out to multiple slots, usually just a single PCIe x1. Other places (such as here: https://www.delock.de/infothek/M.2/M.2_e.html) put it down as PCIe x2 + USB. So it's probably just very strange formatting on the official spec.

[rcmaehl]

2 minutes ago, Zando_ said:

It looks like a weird way of stating it, I can't find any adapter that splits M.2 Key A/E out to multiple slots, usually just a single PCIe x1. Other places (such as here: https://www.delock.de/infothek/M.2/M.2_e.html) put it down as PCIe x2 + USB. So it's probably just very strange formatting on the official spec.

Yeah, I've found that in one other document as well. I'm probably just having an autistic moment but as I'm basically the walking "I don't need sleep, I need answers" meme right now