Quick answer: Force a full link renegotiation by power-cycling the monitor (unplug it for 30 seconds), then disable DSC in your GPU control panel or cap the refresh rate below DSC thresholds — the bug lives in the DisplayPort link training handshake, not your cable.
Why this happens
DisplayPort 1.4 with Display Stream Compression (DSC) does something clever: it compresses the video stream so you can run 4K at 144Hz+ without needing DisplayPort 2.0's bandwidth. The catch is that DSC has to be negotiated every time the link comes up. When you switch away from your PC input to HDMI or another DP source and then switch back, the monitor re-establishes the link — but the PC side often doesn't re-trigger DSC negotiation. The monitor sits there waiting for a compressed stream that never arrives, and you get "No DP Signal from your device."
This isn't a cable problem, and it's almost never a broken port. It's a firmware and driver handshake issue that shows up most on 4K 144Hz monitors (LG 27GP950, Samsung Odyssey G7/G8, Gigabyte M32U), especially when you're running an RTX 30/40-series card with HBR3 enabled. The first time it happened to me on a 3080 Ti feeding a 27GP950, I spent an hour swapping cables before realizing the input swap itself was the trigger.
The fix
- Fully power-cycle the monitor. Not the button on the back — pull the power cord from the wall for a full 30 seconds. DisplayPort capacitors hold state long enough that button-off doesn't reset the link training table.
- Boot the PC with the monitor already on the correct input. Don't switch inputs during POST. Let the handshake complete at cold boot before you touch anything.
- Disable DSC temporarily to test. On NVIDIA, open NVIDIA Control Panel → Change Resolution → set refresh rate to 120Hz (below DSC's 4K/144Hz requirement). On AMD, use Radeon Software → Display → disable "Display Stream Compression" if your driver exposes it. If the no-signal issue disappears, DSC is confirmed as the trigger.
- Update monitor firmware. LG pushed a fix for this exact behavior in firmware 4.12 for the 27GP950. Samsung's G7/G8 got a fix in mid-2022. Check your model's support page — this is the permanent fix for most people.
- Update your GPU driver, clean. Use DDU (Display Driver Uninstaller) in safe mode, then install the latest driver fresh. DSC negotiation bugs have been patched repeatedly in both NVIDIA 5xx branches and AMD Adrenalin 23.x.
- Disable MST if you're not using it. In your monitor's OSD, find DisplayPort settings and turn off Daisy Chain / MST. MST and DSC interact badly on some firmware revisions.
# Quick sanity check from Windows — confirm DSC is active
# Open PowerShell as admin:
Get-CimInstance -Namespace root\wmi -ClassName WmiMonitorBasicDisplayParams |
Select-Object InstanceName, MaxHorizontalImageSize, MaxVerticalImageSize
# Also check current link rate in NVIDIA Control Panel:
# Desktop → Display → view 'DisplayPort link rate' (HBR3 = 8.1 Gbps per lane)
If that doesn't work
- Swap to a VESA-certified DP 1.4 cable. Specifically look for the "DP 1.4" or "DP 2.0" certification sticker. The Amazon Basics 8K cable works fine. Cheap no-name cables often fail link training at HBR3, and DSC makes it worse because it pushes every lane harder.
- Try a different DP port on the GPU. On some 40-series cards, one port has a marginal redriver that fails at HBR3 + DSC combos. Rotating ports is diagnostic, not a fix, but it tells you a lot.
- Set refresh to 120Hz and live with it. If you can't get a firmware fix, 4K/120Hz SDR doesn't need DSC on DP 1.4 (with 8-bit color). You lose HDR headroom at 144Hz, but the signal stops dropping.
- Use HDMI 2.1 instead. If your GPU and monitor both support it, HDMI 2.1 handles 4K/144Hz natively without the DSC handshake dance. The 27GP950 and most current 4K gaming monitors have both.
- RMA the monitor if symptoms persist across firmware, cables, and GPUs. Occasionally the DP controller itself is bad. If a second known-good PC shows the same behavior on the same input swap, that's your evidence.
Prevention
Once you're stable, don't switch inputs while the PC is awake. That's the trigger for 90% of these cases. Either leave the monitor on DP permanently, or put the PC to sleep before you flip to console. Also set your monitor OSD's "DisplayPort Version" explicitly to 1.4 rather than "Auto" — auto-negotiation is where things get flaky. Do those two things and this bug basically stops happening, even without a firmware patch.
One more thing: if you're running a KVM in the chain, add that to the suspect list. KVMs that don't properly pass HBR3 + DSC handshakes cause this exact error more than any monitor or GPU does on its own.