First up, we have the HDMI connector, which is served by that same mux chip as before and is actually an external connector. Tapping it at the connector’s end would be possible, but very inconvenient and is really a last resort. It would also need us to convert HDMI back to DisplayPort which would be sketchy and more expensive. This is pretty much a last resort.

Second, there’s the 2-lane eDP connection served straight from the CPU package. You can’t mix and match lanes from different DisplayPort signals, so this is pretty much irrelevant to us.

Third, there’s the DisplayPort docking signal served by the mux chip. As mentioned previously, this is also not really feasible, although I’m sure some users would prefer a cheaper (but more difficult to install) mod that got rid of the docking port rather than getting rid of HDMI. Personally though, I’d prefer to keep my docking port.

Fourth, the USB-C port on the T470 is both capable of Thunderbolt 3 and DP Alt Mode, which means that a full 4-lane DisplayPort signal has to be made available to it. This was a real possibility here! It would take away the DisplayPort signals from Thunderbolt/USB-C, but finally we’ve got a compromise that I’m willing to make. Unfortunately for us, the block diagram is actually incorrect; the Alpine Ridge TB3 controller receives those DisplayPort signals as DDIx4, not DPx4, so we can’t tap the input, not to mention the fact that the TB3 controller is SMT.

What about the output, though? Sadly, the signals that get sent to the USB-C connector are actually determined by the TB3 controller, which determines whether to send DP, TB3, or USB 3.0. We could theoretically fool the TB3 controller into always sending DP, but it would be a bit of a mess, and we would still lose an external connector. Is there another way?

As it turns out, yes, there is. I left a couple of blocks unblurred in the block diagram above, and while they seemed uninteresting at the time because they don’t carry DisplayPort, it turns out they do actually have DisplayPort. The mux chip from before actually sends a third video signal out to the “WiGig” slot. WiGig is a technology that allows special WiFi cards to pass DisplayPort data wirelessly. They receive these signals directly; they aren’t encoded. I believe they’re always present since these signals come straight from the mux chip. But the most important thing?

They get sent right to the fucking M.2 slot.

This was both the moment I knew this mod was possible, and the moment I thought I was incredibly stupid. I was way overthinking this. We don’t even have to solder!

For a brief recap, there used to be a lot of different connections on motherboards for expansion slots. On laptops, there were mainly two — mSATA and Mini PCI-E. They both shared the same physical slot, but their electronic signals were vastly different, and were incompatible. mSATA slots provided one SATA lane. mPCI-E slots provided one PCI-E lane and one USB 2.0 port. mPCI-E slots were mostly used for WWAN and WLAN (Cell and WiFi, respectively) cards, while mSATA was used for SSDs. Both of these standards have since been replaced by one that tries to be universal. It’s called M.2, or in the early days “M.2 NGFF”, which meant Next-Gen Form Factor. M.2 slots have different ‘keys’, or notches in the slot that designate what each slot is capable of. There are a number of different slots:

A-Key: PCI-E x2, USB 2.0, I2C, and DP x4 B-Key: PCI-E x2, USB 2.0 + 3.0, SATA, audio, UIM, HSIC, SSIC, I2C, and SMBus E-Key: PCI-E x2, USB 2.0, I2C, SDIO, UART, and PCM M-Key: PCI-E x4, SATA, and SMBus

M.2 slots, by spec, can only be keyed for one type. However, cards can have multiple keys, allowing them to be inserted into multiple different types of slots. For instance, all NVMe (PCI-E) based SSDs use M-Key, so they have the most available bandwidth, but SATA-based SSDs are often keyed as B+M, so they can go into both B and M slots. WLAN cards are usually A+E. This allows them access to PCI-E, which they use for WiFi, USB 2.0, which they use for Bluetooth, and for Intel cards, DP x4, which they use for WiGig. WWAN cards exclusively use B key, which allows them to access the SIM information via the UIM available to that slot.

The T470 has either two or three M.2 slots depending upon how you have it configured. There’s an A-key slot for the WLAN card, a B-key slot for the WWAN card, and there’s a 2.5" bay that can either be used for a SATA drive or an M.2 M-key drive with an adapter.

The T25 comes with the WLAN slot populated and the 2.5" bay has an M.2 M-key SSD in it, with the aforementioned adapter. Earlier T25 models came with WWAN cards, and Lenovo sends them out for free upon request, but later T25 models do not have one.

Getting back to the mod — we need that A-key slot for its DP connections. We have two choices; either use a ribbon cable to steal the DP lanes from the A-key slot and leave the WLAN card in-place, and put the mod PCB in the WWAN compartment, or find a way to adapt the WLAN card for the B-key WWAN slot (which has all the needed electrical signals) and use the A-key slot for ourselves.

So yeah. This is possible and I’m talking with Nitrocaster to do everything I can to make this happen. It’s also a LOT cleaner than the X220 Nitrocaster kit, because it doesn’t require soldering, doesn’t compromise the dock connector, and only needs the WWAN sacrifice. The mod would literally just be comprised of an adapter to move the WLAN card, an M.2 card that was the mod itself, and maybe a ribbon cable to connect to the onboard eDP signals (so we can have brightness control and such). The M.2 card would have a regular eDP header for new panels.

God, I’m excited.