Getting 4K at 120Hz out of the Steam Deck

[krizzle]

Thought I’d share my experience.

TL;DR: only possible in Windows at the time of writing.

I wanted to drive my new LG TV at 4K and 120Hz, mostly for the novelty of it. The steam deck was the only source device that I had that could drive such a resolution.

I bought the 8K Cable Matters 201348 video adapter for $50 off Amazon censored claim to run 4K at 120 Hz as well as pass full 100 W power delivery type C. It mostly delivered on these promises but required a firmware update[kb.cablematters.com].

I was disappointed to see that, even after hooking up the adapter and cable to the TV, Steamdeck would not see 120 Hz as a possible output mode at 4K. I read somewhere that it’s only possible to do so on Windows right now.

I followed Wagner’s amazing guide on how to get Windows running off of dedicated SD card[wagnerstechtalk.com] on the steam deck.

Finally, after many hours ahead is 4K 120 Hz image being driven by the steam deck successfully from within Windows.

Practicality? None. Satisfaction? All of it.

[Balderick]

Thanks for sharing. It very good to know a solution for Deck in Dock Mode working to its full potential is available.

[krizzle]

I should note, the Steam Deck's USB-C / PD implementation seems rather broken.

It can't charge at full rate from 60 and 89W Apple Type-C bricks. I think this is because it expects 45W @ 15Vx3A, which most (but not all!) Apple bricks cannot provide. They can do 20V just fine though... and even though the brick that ships with the Steam Deck is capable of 45W @ 20Vx2.25A, it seems to negotiate to the lower 15Vx3A PD contract. Lame.

Also, the Steam Deck cannot power the 8K Cable Matters 201348 video adapter via USB-C's VCONN provision[www.allaboutcircuits.com] ... it's *supposed* to give up to 1W via one of the CC1/2 pins to the dongle that's plugged in. However, with the Steam Deck and the CableMatters dongle, without a separate brick powering the dongle via its dedicated Type-C PD power plug, the dongle just blinks its LED and power cycles. So the dongle must be used with a power supply.

USB-C and PD is hard, Valve. I get it. But I expected a wee bit more compliance and validation from you guys, given that the standard has been around since 2015.

I also confirmed this behavior is consistent between Windows and Linux/SteamOS... implying this likely isn't a driver update issue. Just poor spec compliance.

[Balderick]

Yes, using Deck with dock that has its own power supply is a no brainer. The battery in Deck would last less than half an hour in dock mode otherwise. That is if Decks battery can even provide enough power for Deck to render higher than native display res and refresh rates in dock mode.


The latest patch notes for preview channel show Valve are working hard to get Deck in dock mode working better.

This video shows the resolution issues are nearly fixed but Deck goes in to low power mode and locks everything to 30 fps/hz.
https://www.youtube.com/watch?v=PiSHpylp4GE

So you did well to get 4K @ 120 hz working in Steam for windows though the creator of that video did read out the latest fixes in preview channel also need Steam client beta he never confirmed or showed his Deck was using Steam client beta after applying the preview channels update and ran into the 30 fps lock thing. This very well also could be related to the points you raise about how Deck handles power when in dock mode.

[Brohands McSmooth]

What did you run at that resolution? Any games? Video? Just Desktop?

[Bratty Patty]

Originally posted by Brohands McSmooth:

What did you run at that resolution? Any games? Video? Just Desktop?

He already wrote that he does it only to show thats possible. No Game will run with 4k and 120Fps on the Steam Deck. Even the new Console generation cannot run this in common.

[Balderick]

https://www.youtube.com/watch?v=MXLcaGNp8GY

Both consoles use HDMI 2.1 to give 4K @ 120 hz


Deck uses usb-c with DP 1.4 alt mode to give 4K @ 120 hz when in Dock Mode.

Some cloud gaming services support 4K or 1440p @ 120 hz stream so if Deck can not play games natively there are other ways to get more out of the Deck.

[KingzWayz]

Originally posted by Brohands McSmooth:

What did you run at that resolution? Any games? Video? Just Desktop?

Many amazing 2D Games runs easy at 4K 120fps. Also with FSR 2.X its possible to render at 720p, than output 4K FSR Ultra Performance.

To have the possiblity to put out 4K 120Hz its very important!
We all know very demanding Games dosnt run at native 4K 120fps.
But to cap it at 4K 60Hz is a pain!

[eliw00d]

I, too, wanted to get 4K 120Hz out of my Steam Deck for streaming from my PC via the Moonlight app to my TV. I actually bought the same hub but ran into the same issues as you where neither game mode nor desktop mode allowed me to select anything higher than 4K 60Hz. I talked to both Cable Matters and Valve. Cable Matters said a connected device would need to support DP 1.4 and Display Stream Compression. I asked Valve if the Steam Deck supported that and this was what they told me:

The Deck only support 4K@120Hz with docks that don't support USB3, only USB2. Type C Bandwidth is shared between USB3 and Display Port and 4K@120Hz is only possible when all the bandwidth is dedicated to video. Also, you The best you can do with a DP to HDMI cable out of the official dock is 4K@60. You need pure Display Port all the way to the monitor to get 4k@120hz.

My TV doesn't have Display Port and I'm sure many TVs don't, so I ended up sending the hub back.

I know this is an edge case since the Steam Deck was designed for lower resolutions but honestly it works really well as a new Steam Link when not being used as a handheld. Hopefully there is a way to do it eventually!

[rip3rs]

I have not tested yet but I believe https://www.benq.com/en-us/docks-hubs/becreatus-dock/gr10.html does work it has HDMI 2.1.

https://youtu.be/v0ebZ3XBn14?si=UcpnsDfB3S6JsEUL