6 Posts
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2940
November 20th, 2021 01:00
Video out from USB-C port on Dell Precision 3530
Hi,
I have a Dell Precision 3530 with a multi-monitor setup. Monitor 1 is a 2560x1440@65Hz, and monitor 2 is a 3440x1440@100Hz. My laptop connects to a USB-C dock (Lenovo ThinkPad USB-C Dock Gen 2), which connects to monitor 1 via DP and monitor 2 via HDMI.
However, I'm having trouble getting full resolution/refresh rates on them. In Windows 10, monitor 1 only shows a max of 1280x720, and while monitor 2 runs at 3440x1440, the refresh rate is only 50Hz. Both the dock, monitors and cables are tested in the same setup on another Lenovo Thinkpad T14 Gen 2 laptop with Intel Iris Xe graphics to support the stated resolutions/refresh rates, so they should work.
My Dell should also support higher resolutions since it has a Quadro P600. I'm wondering if for some reason, it's defaulting to the UHD 600 integrated graphics which is resulting in the lower resolutions/refresh rates?
jphughan
9 Legend
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14K Posts
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November 20th, 2021 05:00
@goister The problem is video bandwidth. The T14 Gen 2 with the Xe GPU built into its Core 11th Gen CPU supports DisplayPort 1.4/HBR3 over USB-C. The Precision 3530 with its older Intel 630 GPU built into its Core 8th Gen CPU only supports DisplayPort HBR2 over USB-C. The NVIDIA GPU is not directly wired to the display outputs, so it doesn't come into play here. It operates as a render-only device when needed through technology called NVIDIA Optimus, which involves passing video through the Intel GPU to output to the displays. So the Intel GPU's capabilities are what matter here. And it's capable of running up to triple 4K 60 Hz displays, so resolution isn't the issue.
With a USB-C dock, the USB-C link will be configured to support both video and USB 3.x data. Carrying the latter requires cutting bandwidth for the former in half over what the USB-C port could provide if it was only being used for video, such as with a USB-C to DP cable or a USB-C MST hub. Half of an HBR3 link as exists on your T14 Gen 2 is enough to run your display setup. Half of an HBR2 link is not, in fact I think it's only enough to run 3440x1440 at 60 Hz, not even at 100 Hz. But you're trying to run an additional display.
However, the Precision 3530 could optionally be ordered with Thunderbolt 3. And that is standard on the T14 Gen 2 (although you have to use the USB-C port inside the funky proprietary connector, which is the only one that supports Thunderbolt, not the one closer to the rear edge of the system). If your particular 3530 has Thunderbolt, then if you were to get a Thunderbolt dock, such as the Lenovo ThinkPad Thunderbolt 3 Dock Gen 2, then both of your systems would be able to run your display setup from that dock, since that dock when paired with your 3530 would be able to tap into 4x more video bandwidth and would therefore allow both systems to run up to dual 4K 60 Hz.
If you don't want another dock and/or you don't have that option because your Precision 3530 doesn't have Thunderbolt, you would need to connect one of your displays directly to your 3530's HDMI output so that its bandwidth requirements didn't have to be met over the dock connection.
goister
6 Posts
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November 20th, 2021 22:00
Thanks @jphughan that might be the case. I remember using the same laptop on 2 different monitors (another 2560x1440 over USB-C, and a FHD one on HDMI), and it displayed both at full resolution. I'll try connecting the monitors separately and see if it works.
jphughan
9 Legend
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14K Posts
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November 20th, 2021 22:00
@goister Happy to help. It’s definitely the case. I’ve fielded so many threads where people ask about this issue that I’ve lost count. Connecting the displays separately would work because in that case you wouldn’t have to meet the bandwidth requirements of both displays over a single link between the system and dock that with your combination of equipment won’t be sufficient.
goister
6 Posts
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November 21st, 2021 00:00
Thanks. I just checked by connecting the 2560x1440 monitor via the Lenovo USB-C dock, and the 3440x1440 monitor via HDMI, and was able to achieve max 2560x1440@75Hz on the 1st monitor and 3440x1440 on the 2nd one. Though the 100Hz option was available on Windows, once I enabled 100Hz option, the monitor blacked out, so seems like I'm stuck at 60Hz. Might be a problem with my HDMI cable?
jphughan
9 Legend
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14K Posts
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November 21st, 2021 06:00
@goister Yes, that is a possibility. The specs of that system indicate that the HDMI port supports 1.4 when it only has an Intel GPU and 2.0 when it has a discrete GPU as you do. There are cables rated specifically for HDMI 2.0. Sometimes cables not rated for 2.0 can perform above their rated spec but not quite as well as required. I remember a friend getting an Xbox One X, which supports 4K 60 Hz. For convenience, he tried reusing his existing cable. It mostly worked, except he saw a brief signal dropout every minute or so. Replacing the cable resolved it. So that may be what’s happening here.