Do you need DisplayPort 2.1 for 4K 240Hz? Bandwidth and cable guide

How this is calculated

UHBR 10 (38.69 Gbps) and UHBR 13.5 (52.22 Gbps) can't reach this mode uncompressed and fall back to DSC. UHBR 20 is the tier you actually need for 4K 240 Hz HDR without any compression. Its per-cable physical reach is shorter than UHBR 13.5, which is why only certified-40G DisplayPort 2.1 cables (usually under 1 m) can sustain this bandwidth. This is the highest-fidelity desktop gaming mode available outside of HDMI 2.2 (96G) territory.

Verdict

4K at 240 Hz with 10-bit 4:4:4 HDR needs 66.9 Gbps, 87% of DisplayPort 2.1 UHBR 20's 77.37 Gbps effective data rate, so it fits natively without DSC. The lower UHBR tiers can't reach this mode uncompressed: UHBR 13.5 (52.22 Gbps) and UHBR 10 (38.69 Gbps) both fall back to DSC. UHBR 20 is the tier that actually delivers 4K 240 Hz HDR natively, and its physical reach is shorter than UHBR 13.5, which is why certified 40G DP 2.1 cables reliably sustain this mode only under about 1 meter passive or 3-5 meters with an active optical cable. That's the price of native uncompressed 4K 240 Hz, and it's why DP 2.1 UHBR 20 exists.