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DMwilliams
Beginner
134 Views

I want 30hz, but can't find figure out how

I have a new Lenovo and tried ordering a USB-C hub which has an HDMI output. The video never responded. Looked up the documentation and USB-C hubs only support video at 30hz. In fact, as best I can tell, it's not just this one, it's all of them.

I cannot find any setting that allows me to get that low. 50hz seems the slowest I can get. I just want the second screen for Excel and PDFs so 30hz is no hardship. 

Any help? 

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5 Replies
n_scott_pearson
Super User Retired Employee
125 Views

I am unsure what your problem is. I was especially confused by your mention of 50Hz. Please explain yourself better.

With this hub device, I can run 2K@60Hz  or 4K@30Hz:  https://www.amazon.com/Falwedi-Multiport-Adapter-MacBook-Laptops/dp/B083FBYP9B.

With this adapter, I can run 2K@60Hz or 4K@60Hz: https://www.amazon.com/StarTech-com-USB-HDMI-Adapter-HDR/dp/B07N8RFW86.

The difference between this hub and this adapter is the hub's support and use of USB. This limits the lanes available for video. With most Intel processors, which only support DisplayPort 1.2, this means only 4K@30Hz will be achievable. With one of the new 10th gen processors that supports DisplayPort 1.4, however, this limitation should not exist and 4K@60Hz should be achievable (the Falwedi documentation actually states that 4K@60Hz is supported if DisplayPort 1.4 is supported).

...S

DMwilliams
Beginner
96 Views

@n_scott_pearson , I returned that hub and ordered a new one from Anker this time. Claims to run UHD/4K at 60hz. Still nothing. 

Tried a brand new HDMI 2.1 cable as well. Still nothing. 

When I plug the monitor straight into the computer it works, Win10 sees it. When I plug it in through the hub, nothing. I feel like it's a setting. I don't think it's a hardware issue.  Every review I see online for just about any hub, the reviewer plugs it in and it just loads. 

Frustrating. 

n_scott_pearson
Super User Retired Employee
91 Views

Let me summarize what we know,

While the processor's DisplayPort 1.2 output channels are capable of supporting 4K@60Hz,  there are 'complications'. If you are using a simple USB-C-to-DisplayPort or USB-C-to-HDMI adapter, you *can* get 4K@60Hz (presuming good quality adapter). When talking about any kind of hub, however, the limit drops to 4K@30Hz. Why? Well, this is because some of the lanes used for DisplayPort 1.2 communication are also used for USB and, if USB is being supported in the hub, these lanes are then not available for DisplayPort.

Now, we regularly see hubs claiming 4K@60Hz support, but when we hook them up, only 4K@30Hz can be achieved. What isn't being said (or is in small print) is that these hubs can only support 4K@60Hz when the processor has support for DisplayPort 1.4. DisplayPort 1.4 uses twice as many lanes in the USB-C connector and these extra lanes do not conflict with USB usage.

Ok, knowing all that, you *should* be able to get 4K@30Hz working off the hub. I do not understand why not. Do you have any 1080P monitors? I am curious to know if one of these will work.

...S

DMwilliams
Beginner
88 Views

@n_scott_pearson Good thought... same result. Took my laptop over to the TCL television. Plugged in the HDMI directly to the laptop and the TV duplicated my screen in a matter of seconds. Plugged the HDMI into the hub... nothing. 

2 hubs

3 screens

2 cables

Same result. 

n_scott_pearson
Super User Retired Employee
84 Views

I bought this basic hub: https://www.amazon.com/gp/product/B083FBYP9B a few weeks ago. As expected, it only supports 4K@30Hz. [Aside: Which was good enough that my son walked off with it yesterday (I ordered another; it's only US$20).]  Anyway, on a small, folded piece of paper (I refuse to call it a user's manual) that they included with the hub, Falwedi explains that DisplayPort 1.4 is necessary for 4K@60Hz. Anyway, now that you've shown that a non-USB device works, it would be interesting to test with this simple hub to see if it will also work or whether its support of USB is enough to kill it. Yea, it doesn't support the two monitors you wanted, but, well, baby steps...

...S