I recently bought an ASUS PG34WCDN and am trying to run 3440×1440 at 360Hz with 10-bit color while keeping Display Stream Compression (DSC) turned off. When DSC is disabled, the display only offers 6-bit color. I'm using an AMD Radeon RX 9070 XT, which supports DisplayPort 2.1, and I'm using the DisplayPort cable included with the monitor. I've also tested another cable, confirmed that the included cable works for other owners, and installed the latest monitor firmware and graphics drivers. Is this a bandwidth limitation, or is something configured incorrectly?
2 Answers
That behavior is expected at this resolution and refresh rate. 3440×1440 at 360Hz with 10-bit color needs more uncompressed bandwidth than the graphics card’s DisplayPort connection can provide. With DSC disabled, the system compensates by dropping the color depth to 6-bit. DSC is designed for this exact situation, so you need to leave it enabled to use both 360Hz and 10-bit color without sacrificing the refresh rate.
Having DisplayPort 2.1 doesn’t necessarily mean every available link speed is supported. The RX 9070 XT uses UHBR13.5, which provides up to roughly 54 Gbps, while the monitor supports the faster UHBR20 mode at up to 80 Gbps. Uncompressed 10-bit 3440×1440 at 360Hz requires more bandwidth than the card can deliver, so DSC is necessary with this GPU.
I didn’t realize DisplayPort 2.1 had different UHBR tiers. The monitor can support UHBR20, but the 9070 XT’s UHBR13.5 link is the limiting factor.
That clears it up. I’d seen someone say they were running it successfully, but I’ll turn DSC back on.