AFAIK the problem with HDMI expansion power drain is still an issue.
Maybe it could be solved with hardware mod. The mod would cut the power off from card, when HDMI plug is not connected.
I think about adding transistor to usbc power line, with gate connected to HDMI HPD pin.
The problem may that pin may be used also for other purposes in newer versions of HDMI (HDMI Ethernet and Audio Return Channel). However, these features are rather not relevant to laptop and maybe they are even not supported by this card.
What do you think about this idea? Should this mod work? Do you have better idea how to do it? Should I worry about HPD changing its state after connection for other purposes?
I haven’t got framework yet, and I don’t know how exactly this module looks like. Is it possible to disassembly it to make modifications? I haven’t seen any screws on pictures available.
We’re actually currently in the process of validating something similar to this, but at a firmware level to drop off of USB-PD when there is no cable connected. There was a very early firmware version of this with the DP Expansion Card that we shared as a beta last year.
I think @nrp was referring to change for HDMI/DP card only. They consume much more power than USB A AFAIK. And after this change they probably still at least the same amount of power as USB A card.
I don’t think there is software mod for USB A, there is no electronic there only one pul-down resistor. I think the only power loss is on this resistor when nothing is connected, and it would be 5 mW if I calculated correctly.
That actually is present in the most recent Beta BIOS’s, but there is a separate Intel CPU bug that results in it not working if there is also an HDMI or DP card present. That led us to investigate also doing the changes on the HDMI and DP card firmware side that are currently in development.
@nrp would it be possible to exchange the old hdmi card for a new one so that you guys can do the refit and re-sell? Not for free mind you but in the spirit of recycling.
Maybe it isn’t worth the shipping though =)
Otherwise i’m going to buy the new hdmi port and trash the old one as I have no use for it.
I just broke an expansion card attempting the mod. I’m fairly experienced with surface mount soldering, but the pads are EXTREMELY small. The pictures in the tutorial make them seem larger than they are. I can usually get by with a magnifying glass and I used a T12 J tip. I easily got the jumper attached to the pin on the chip. Just the wrong one, i went to move it and it was very easy to use too much heat and burn up the pad.
I think I’ll wait for the next revision to buy one already with the fix. Just hoping they’ll be marked or differentiated on the marketplace once they’re released.
I was kind of disappointed that no one gave any numbers, especially given how much better the power consumption is after the mod.
Note that my testing was done with a couple rounds of powerstat so pretty rudimentary. Procedure was to leave module unplugged, run powerstatfor one cycle with the whole system just idle and ensuring the backlight stayed consistent (didn’t dim from lack of use). Plug module in, wait a minute or so for everything to settle, and then re-run a round of powerstat and compare the average consumption during both runs. Repeated pre-mod and post-mod twice. Both tests were with nothing plugged in to HDMI, just it plugged in to the expansion slot.
Pre-mod averaged about 1.5 W at all times.
Post-mod was closer to 0.1 W.
If anyone can do more tests with a real USB power measurement tool, I’d love to see them.
Also, if anyone who comes across this really wants those savings but isn’t comfortable doing the mod, feel free to reach out and I’ll do what I can.