In my workplace, I have a Lenovo T14 laptop(1), connected by USB-C to a 1080p monitor(2) which functions as a docking station - specifically, it's connected to another monitor via DisplayPort out (set in the monitor as "DP Out Multi-Stream=Extend").
This works, but the additional monitor is limited to 1920×1080. When I connect it to a 2k(2560×1440) monitor (HP Z27), I can only set it to 1920×1080, and then the display looks bad because it's not its native resolution.
Question: Is this a limitation of the laptop itself? Or of the monitor? Anything I can do to get the laptop to support these external monitors properly?
What I tried:
- Disable the laptop's built-in 1920×1080 display - same result
- Connect the laptop directly to the 2k(2560×1440) monitor using USB-C - works well. Also tested with 4k(3840×2160, HP Z32).
- Install monitor driver - same result
- Update latest firmware for the 2k monitor (1.0.0.18 Rev.A, shows up on the monitor as LIM293) - same result
- MonitorInfoView correctly shows the max resolution of 2560×1440.
(1) Lenovo T14 Gen1 20S1S3VT1N, with i5-10310U CPU and Intel UHD Graphics (latest drivers 31.0.101.2114), built-in 1920×1080 display.
(2) Philips 243B1, 1920×1080. It connects via USB-C, and then it:
- display the output of DisplayPort-over-USBC on the monitor. Note that it does not include a separate GPU like DisplayLink.
- outputs DisplayPort to an additional monitor via DisplayPort 1.2 daisy-chain
- Has sound-over-USB, Ethernet-over-USB, and a few additional USB ports
Additional Research
I recorded the USB setup using USB Device Tree Viewer
Scenario 1 - second monitor limited to 1920×1080
Lenovo T14 gen1 (Intel UHD Graphics)
Dock monitor: Philips 243B1_27 1920×1080, USB set to USB 3.2
Second monitor, connected to dock monitor using DisplayPort-Out: HP Z27n G2 2560×1440 <<<<< Limited to 1920×1080
|---Intel(R) USB 3.1 eXtensible Host Controller - 1.10 (Microsoft)
| +---USB Root Hub (USB 3.0)
\---Intel(R) USB 3.1 eXtensible Host Controller - 1.10 (Microsoft)
\---USB Root Hub (USB 3.0)
|HS-[2-1]
|---[2-2]: Generic USB 2.1 Hub
| |---[2-2-1]: Generic USB 2.1 Hub
| | |LS-[2-2-1-1]: Avago Pte USB Optical Mouse <<<<< Monitor's USB ports, with some devices connected
| | |LS-[2-2-1-2]: Lenovo Traditional USB Keyboard
| | |HS-[2-2-1-3]
| | |HS-[2-2-1-4]
| | \HS-[2-2-1-5]
| |HS-[2-2-2]
| \HS-[2-2-3]
|FS-[2-3]: MOSART Semi 2.4G INPUT DEVICE - Keyboard, Mouse, 2× HID
(...)
|SS-[2-13]
|---[2-14]: Generic SuperSpeed USB 3.2 Hub
| +---[2-14-1]: Generic SuperSpeed USB 3.2 Hub
| \SS-[2-14-2]: Realtek USB GbE Family Controller - Net <<<<< Monitor's network controller - on USB3
(...)
Scenario2: Monitor switched to USB2, second monitor running at full res
Lenovo T14 gen1 (Intel UHD Graphics)
Dock monitor: Philips 243B1_27 1920×1080, USB set to USB 2.0
Second monitor, connected to dock monitor using DisplayPort-Out: HP Z27n G2 2560×1440 <<<< Running at full res
|---Intel(R) USB 3.1 eXtensible Host Controller - 1.10 (Microsoft)
| +---USB Root Hub (USB 3.0)
\---Intel(R) USB 3.1 eXtensible Host Controller - 1.10 (Microsoft)
\---USB Root Hub (USB 3.0)
|HS-[2-1]
|---[2-2]: Generic USB 2.1 Hub
| |---[2-2-1]: Generic USB 2.1 Hub
| | |LS-[2-2-1-1]: Avago Pte USB Optical Mouse <<<<< Monitor's USB ports, with some devices connected
| | |LS-[2-2-1-2]: Lenovo Traditional USB Keyboard
| | |HS-[2-2-1-3]
| | |HS-[2-2-1-4]
| | \HS-[2-2-1-5]
| |HS-[2-2-2]: Realtek USB GbE Family Controller - Net <<<<< Monitor's network controller - on USB2
| \HS-[2-2-3]
|FS-[2-3]: MOSART Semi 2.4G INPUT DEVICE - Keyboard, Mouse, 2× HID
(...)
Scenario3: Stronger laptop, second monitor running at full res
Laptop: Lenovo T14 Gen2i (Intel Iris XE)
Dock monitor: Philips 243B1_27, USB set to USB 3.2
Second monitor, connected to dock monitor using DisplayPort-Out: HP Z27n G2 2560×1440 <<<< Running at full res
|---Intel(R) USB 3.10 eXtensible Host Controller - 1.20 (Microsoft)
| \---USB Root Hub (USB 3.0)
(...)
| |HS-[1-5]
| |---[1-6]: Generic USB 2.1 Hub
| | |HS-[1-6-1]
| | |HS-[1-6-2]
| | |LS-[1-6-3]: PixArt Lenovo USB Optical Mouse <<<<< Monitor's USB ports, with some devices connected
| | |LS-[1-6-4]: Dell USB Keyboard
| | |HS-[1-6-5]
(...)
\---Intel(R) USB 3.10 eXtensible Host Controller - 1.20 (Microsoft)
\---USB Root Hub (USB 3.0)
|HS-[2-1]
|SS-[2-2]
|SS-[2-3]
|---[2-4]: Generic SuperSpeed USB 3.2 Hub
| |SS-[2-4-1]
| |SS-[2-4-2]
| |SS-[2-4-3]
| |SS-[2-4-4]
| \SS-[2-4-5]: Realtek USB GbE Family Controller - Net <<<<< Monitor's network controller - on USB3
\SS-[2-5]