USB-C hub / dock with 2560x1440@120Hz HDMI capability and ethernet?

[Line_Noise]

Is anyone aware of a USB-C dock or hub that includes both support for 2560x1400@120Hz over HDMI and an ethernet port?

I'll be attaching this to an M2 MacBook Air and there'd be some advantage to either a side attaching dock or one with a reasonably long cable as I use the laptop on a ~15cm stand meaning some of the fixed cables end up dangling.

Really struggling to find good information about higher refresh rate support and it seems 4K/60Hz is often 60Hz even at lower resolutions on these docks.

 

[joevt]

Most USB-C docks that support 4K60 should be able to do 1440p120 since 1440p120 requires less bandwidth than 4K60.

The problem is, USB-C docks only have two lanes of DisplayPort if they can support USB 3.x so it would need to have a DisplayPort to HDMI adapter that can support HBR3 link rate or DSC. HBR3 link rate by itself would be limited to 8bpc (no HDR). DSC would allow 10bpc and HDR except some DisplayPort to HDMI adapters or MST hubs that support DSC can't use DSC to do 10 bpc such as with the CalDigit SOHO which contains an MST hub that can't do 10bpc with DSC. I don't know of a MST hub that can do DSC with 10 bpc. An MST hub can convert 2 lanes of HBR3 to 4 lanes of HBR2 (but 2 lanes of HBR3 is only 75% the bandwidth of HBR2 x4). An MST hub can take DSC input and decompress it for displays or adapters that don't support DSC (but I don't know of a MST hub that can decompress 10bpc).

Use Thunderbolt to get away from these compromises but they are usually triple the price...

 

[ArkSingularity]

Most USB-C docks that support 4K60 should be able to do 1440p120 since 1440p120 requires less bandwidth than 4K60.

I've tested this on a lot of the random USB-C docks I've purchased. The best I ever got was 75hz at 1440p, but the majority of them (much to my surprise) only did 60hz, despite having plenty of bandwidth headroom.

It definitely varies depending on the dock. I definitely recommend doing research on it before purchasing, since good documentation is often very hard to find on some of them. Thunderbolt docks would definitely be able to do it, but that's a very pricey solution to the problem (I'm sure someone has found a regular USB-C dock that can do it and might be able to share, but none of the ones I've tried yet could work at these refresh rates on 1440p. I highly doubt that there are truly none that can do it, but I've had some interesting luck with them.)

 

[joevt]

AllRez can be used to get DisplayPort info (DPCD) for displays, docks, and adapters. It will show link rate and link lanes limits and whether DSC is supported and if macOS has DSC display modes. Some of that info requires using an Intel Mac because the API to get that info on Apple Silicon Macs is different and not public.

 

[ArkSingularity]

AllRez can be used to get DisplayPort info (DPCD) for displays, docks, and adapters. It will show link rate and link lanes limits and whether DSC is supported and if macOS has DSC display modes. Some of that info requires using an Intel Mac because the API to get that info on Apple Silicon Macs is different and not public.

This is very interesting, never heard of this. Thanks for sharing.

 

[Line_Noise]

Thanks for the very detailed info.

I get the feeling that a dedicated video adapter and everything else on the other port might be the simpler solution. More things to carry but finding info on the all in ones seems like getting blood from a stone. A lot of companies just don't seem to know whether their products can or can't drive high refresh rates at all and default to answers about 4K.