DisplayPort 2.1 Cable Problem: RTX 5090 Users Need Certified DP80 for Full Speed

DisplayPort 2.1 monitors may not deliver their full bandwidth without a certified DP80 cable. Nvidia RTX 50 series GPUs automatically reduce link speed when they detect a lower-quality cable. This forces display stream compression (DSC) on, negating the benefit of the higher bandwidth.

Certified DP80 cables required for full bandwidth

DisplayPort 2.1 supports UHBR20 mode, which provides 80 Gbps over four lanes at 20 Gbps each. An uncompressed 4K 240Hz 10-bit signal requires 68.6 Gbps. Without a certified cable, the link drops to UHBR10 at 40 Gbps, which is insufficient for uncompressed high-resolution high-refresh-rate video.

Specifications

• DisplayPort 2.1 UHBR20 bandwidth: 80 Gbps (4 lanes at 20 Gbps each)
• Uncompressed 4K 240Hz 10-bit signal bandwidth requirement: 68.6 Gbps
• UHBR10 bandwidth: 40 Gbps (4 lanes at 10 Gbps each)

Certified DP80 cables are identified by a DP80 logo and listed in VESA's database. Using a non-certified cable forces the GPU to fall back to UHBR10 and enables DSC. According to TechSpot, DSC is visually lossless and indistinguishable from uncompressed in real-world use.

All DisplayPort 2.1 monitors work with Nvidia RTX 50 series GPUs even with lower-quality cables. But only certified DP80 cables deliver true UHBR20 connectivity, according to a translated Quasarzone report cited by TechSpot.

The practical impact is limited because DSC compression is visually lossless. However, users who want uncompressed video for 4K 240Hz or higher resolutions need to ensure they have a certified DP80 cable.