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Jeroen W. Pluimers on .NET, C#, Delphi, databases, and personal interests

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When you need USB 3 downstream ports on your monitor, be wary of LG monitors

Posted by jpluimers on 2024/07/15

After researching the below tweet, I found out that many LG monitors have this limitation on downstream ports, depending on how the upstream USB-C port is connected:

Their manuals phrase it like this:

  • When the USB C-C cable is connected between Upstream port of monitor and Host PC, the Downstream port of
    monitor support USB 2.0 device.
  • When the USB C-A cable is connected between Upstream port of monitor and Host PC, the Downstream port of
    monitor support USB 3.0 device.
    However, Host PC must support USB 3.0 function.

This means that in USB C-C land (for which Apple was basically a driving force, but nowadays many laptops only have USB-C connections) your monitor downstream ports are limited to USB 2.0.

If I read the various comments correctly, the additional limitation is that in the USB C-C case, the downstream ports are non-powered.

Which means I will avoid LG monitors at all cost.

Tweet: [Wayback/Archive] anna (arar) meow 𓃠 on X: “i have this monitor connected to my mac with a single USB C-C cable. why can’t i have USB 3.0 speeds on the downstream ports??? why does it work with the USB C-A cable?? is there a way around it? or is there just not enough bandwith for both video and these silly ports?”

[Wayback/Archive] GSDuhEaaUAAmjv_.png (550Γ—602)

@meowkoteeq Bandwidth issue 100%. 3440×1440 @ 160hz is 24Gbps (8 w/ DSC). Then saving a quick buck to not have appropriate bandwidth ports (USB4 or just higher specced 3.2gen2) and you have the salad. @meowkoteeq C-A doesn’t (ordinarily, when following the spec) support DP so you no longer need the bandwidth reservation, ergo you get full bandwidth downstream.

[Wayback/Archive] Thread by @FPSlime on Thread Reader App – Thread Reader App

References:

Note that the monitor from the original tweet has some not so nice reviews at [Wayback/Archive] LG 34WP75C-B Zwart – Reviews – Tweakers.

--jeroen

This entry was posted on 2024/07/15 at 18:00 and is filed under Displays, Hardware, LG Monitors, LifeHacker, Power User, USB, USB-C. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.

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