I was given a Lenovo Legion 5 work laptop and a dual-monitor KVM switch for my work-from-home setup. The monitors are two Samsung Odyssey G5s: the newer left display supports 165Hz, while the older right display supports 144Hz. The KVM has DisplayPort inputs for up to three computers and advertises support for 8K at 30Hz, 4K at 144Hz, and USB 3.0, although I cannot identify the brand or exact model.
The laptop connects to the KVM through a USB-C-to-dual-DisplayPort adapter plugged into the laptop's USB-C port marked for USB-PD. My personal desktop works correctly with both monitors through the KVM. However, the laptop only produces an image on the 144Hz monitor. Windows detects the second monitor and shows it as active, but that display reports no signal. I have swapped the cables and tried connecting the laptop directly to the monitor without the KVM, but the problem remains. The laptop should support 165Hz, and changing refresh-rate settings has not fixed it. What else should I check?
3 Answers
Since the problem also occurs when the laptop is connected directly, the KVM may not be the only issue. Check the monitor's refresh-rate and overclock settings. A display set to a mode the laptop, adapter, or cable cannot actually deliver may appear in Windows but still show no signal. Try a conservative resolution and refresh rate on the problem monitor, then increase them gradually.
The entire signal path needs to support the required bandwidth: the laptop's USB-C video output, the dual-DisplayPort adapter, the DisplayPort cables, and the KVM. For two high-resolution, high-refresh displays, look for a reliable adapter and VESA-certified high-bandwidth DisplayPort cables, ideally with support for DisplayPort 1.4, DSC, and proper EDID handling. An inexpensive or poorly specified KVM can also misreport display capabilities even if it works with the desktop.
The KVM itself may simply be the weak link. Generic switches sometimes fail with mixed refresh rates or dual-monitor setups, despite listing high maximum specifications. A better-quality dual-monitor KVM with clearly documented DisplayPort bandwidth and EDID emulation may be necessary, especially if the same laptop-to-monitor connection fails only when using this particular adapter or display mode.
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