Recently while trying to answer this myself, I found a lot of discussion on this subject, but no definitive answer.
M.2 B Key sockets have a variety of possible modes as defined by the NGFF specification:
The second to last mode “RFU” (Reserved for future use) is defined by Dell as:
I am unsure what HCA stands for, but have seen it printed on the silkscreen of some of my earlier latitude models. Clearly it is some kind of proprietary device that requires one PCIe lane. It may stand for Host Channel Adapter – Implying some kind of non-NVMe PCIe SSD (i.e. has an Option ROM).
None of this tell us anything about what Dell have actually implemented on thier WWAN slots, neither does their tech support, or any of their documentation. I found myself eyeballing the traces extending from the socket, but even this was inconclusive as a lot of them are fed up from vias under the socket.
It’s given that it’ll have SSIC/USB 2.0 because almost all WWAN cards use those interfaces, but what of the others?
Fortunately there’s no need for any further conjecture because the schematics for these models are floating around the internet, so let’s answer that question definitively.
The above diagram covers models 7280, 7380, 7480, 7490 and likely others too. So there we have it. The interfaces on the WWAN socket are:
- USB 2.0
- SSIC (Chip-to-Chip USB 3.0)
- PCIe (Permanently disabled in BIOS)
Just because we know what interfaces are there, we still don’t know what kind of peripherals will actually work. For example – if a socket can accept WWAN-PCIe – SSD-PCIe should also be no problem as the required connections are all there, however those devices will have their configuration pins tied differently, allowing the BIOS to determine exactly what’s attached.
This allows manufacturers (for example) to allow PCIe WWAN cards, but disallow PCIe SSDs. On top of that, just because an interface is there, it doesn’t mean that it’s actually enabled.
This turns out this is the case for my Dell Latitude. While the PCIe is there, it cannot be used because the port on the root complex is disabled in the BIOS, and there’s no way to enable it (without hacking the BIOS). I was able to confirm this by testing out a variety of B-Key PCIe devices, none of which were detected (even when strapped as WWAN-PCIe).
A dick move by dell, but given how rare WWAN cards requiring PCIe are, they had no reason to enable it, and my experience from owning previous models is that they’re pretty good at tying up loose ends like this.
Short of hacking the BIOS, or building a new type of USB 3.0 card from scratch, only WWAN cards will work in the WWAN slot.
Yours may differ
Older Dell models did have SATA+PCIe in the WWAN socket, but this is not the case for more recent units. The story will inevitably be different for other manufacturers.Posted in PC & Software
20 thoughts on “Does the Dell Latitude M.2 WWAN socket have the SATA interface on it?”
Thank you for your information.
I am using a Dell 7490 and interested in this potential advantage.
Not sure if you may already know, there is at least one guy successfully put a M2 SSD 2430 into WWAN slot.
Your comment, please. Thank you 🙂
Where does it say that?
Sorry, I copied the wrong links.
This link is what I would share:
The user PrecessSoft did success with a Dell 7390.
The user JOcen may also got that too.
In that particular example the silkscreen is clearly marked “SSD” as well as “WWAN” – meaning Dell have left the PCIe port enabled – so I’m not surprised it’s working. In the case of 7480 + 7490 there is no such mention. 73xx must have been the last model to allow this.
Thank you for pointing it out :).
I don’t understand why Dell did that.
I believe the reason (possibly) is because SSDs in that form factor have two PCIe lanes. While Dell could have enabled the first lane to allow it to work, the second land on the SSD falls on the same pins as the SSIC interface, which from my experimentation causes it to go ape shit, so you’d have to try insulate or remove the pins on the second lane.
Perhaps this could have been resolved using the config pins but that would potentially have added cost, for an obscure and esoteric use case.
https://youtu.be/KWlDqz5JkpA this 5490 working on wwan and I tried in my 5490 both Nvme and Sata detached
I am sure that some models still support this – however it’s not the case for the models I mention on this post.
Many thanks for this article. I was thinking about the same question.
Why the down-vote people! This is a good question I support it. I have a dell P11F witch does not accept a mSATA ssd and an lenovo e520 witch does. Now the reason to this is that some manufactures have a slot that can be mSATA and mini PCIe based on bios configuration. botenvouwer Dec 13 ’14 at 15:37
Interesting post, especially this:
Older Dell models did have SATA+PCIe in the WWAN socket, but this is not the case for more recent units. The story will inevitably be different for other manufacturers.
Doyou happento knowif the Latitude E5470 falls into this “older” category?
Just for info: I have successfully upgraded several 5480 with an additional SSD in WWAN port. so if it works with 5480, I’d assume it should for it’s predecessor 5470.
Sorry for my bad English.
Does the 7480 now support ssd wwan? and can I boot from it?
I was able to add a 2 lane pcie3x2 western digital m plus b key into the b key socket wwan of my dell latitude 5500. while the nvme card is recognized by both windows and linux os in both operating system i get and usb error. windows device managers pops up an error every few seconds something like unable to enable usb port. if i boot in linux the error is also present and say unable to reset usb hub 2 port 5 maybe the cable is bad?…Anyway ignoring those errors the storage device is completely usable. I am assuming the error happens because one pci lane lands on usb pins on the socket. Can anybody confirm that? and if that is the case what pins on the hard drive should i tape to make like the second pci lane wont make contact with the socket basically eliminating one pci express lane?
You are correct. You’ll have to cover pins 21,23 27,29 as are stated on the schematic snippet I posted. The question is what with. Kapton tape might be a good starting point. Whatever it is would have to be insulating, very thin, and very strong otherwise there’s a risk of it not working, or damaging the pins in the socket.
thanks for valuable information.
I want to ask that my Dell latitude e7250 wwan port will support nvme 2242 ssd likeKingspec 2242 NVME/PCI-E SSD, M KEY B+M KEY or Toshiba RC100?
You should have a look here: https://www.thewichitacomputerguy.com/blog/how-add-second-hard-drive-dell-latitude-5580-or-5590
Also i proved wrong a few other dell techs and forums when i put into my Dell Latitude 5480 not 2 but 3 drives .
I am using the Dell Latitude 7390 model which has similar issue. I attempted number of M.2 PCIe SSD 2242 variant on the WWAN slot and it didn’t work. I wasn’t aware of the fact that Dell willingly disabled the PCie port on M.2 slot. Not so surprisingly “SSD” was not marked on the motherboard either. It took me little while to grasp the whole idea. Thank you.
Very useful information. If WWAN is locked down via BIOS, could you post which BiOs version you tested with?