GeForce RTX 4090 Can't Handle Samsung's Odyssey Neo G9 240Hz Monitor: Limited to 120 Hz

Samsung's gigantic 57-inch Odyssey Neo G9 display is certainly one of the most anticipated gaming monitors of the year. Impressively, it supports an ultrawide resolution of 7680x2160 at a refresh rate of 240 Hz. But it appears that the gamer's dream display cannot be handled by one of the world's highest-performing gaming graphics cards, namely the Nvidia GeForce RTX 4090. Whether using DisplayPort 2.1 or HDMI 2.1 connection, some limitation seems to be present, a review of the display by QuasarZone revealed.

An Odd Limitation

For now, the only graphics cards that can handle a 7680x2160 resolution at a refresh rate of 240 Hz with Samsung's curved 57-inch Odyssey Neo G9 are AMD's Radeon RX 7000-series that support a DisplayPort 2.1 with UHBR 13.5 (and offering a 54 Gbit/s of bandwidth). Meanwhile, the review by QuasarZone indicates that AMD's Radeon RX 7000-series boards can also support 7680x2160 at 240 Hz using HDMI 2.1 when used with a proper 48G cable. By contrast, neither Nvidia's GeForce RTX 40-series GPUs nor Intel's Arc A700-series GPUs could support this resolution at this refresh rate using any kind of connection, according to QuasarZone.

Such a limitation is very odd, and its reasons are unknown. However, there could be restrictions in Intel and Nvidia GPU display pipelines or certain limitations in firmware or software.

Possible Reasons

Samsung's curved 57-inch Odyssey Neo G9 display is essentially two 4K 240 Hz displays glued together. Transferring an uncompressed 4K stream with 10-bit per color at 240 Hz requires 54.84 Gbit/s of bandwidth, and transferring two such streams requires 109.68 Gbit/s of bandwidth. The highest bandwidth one can get today from a single display connection is 77.37 Gbit/s (using DisplayPort 2.1 with UHBR 20) or 48 Gbit/s (using HDMI 2.1), so whatever connection is used, Display Stream Compression (DSC) technology is required.

DSC can compress any image to 8 bits per pixel (bpp) without a perceptual loss in image quality. This results in a 3:1 compression ratio for a 24 bpp image or a 3.75X compression ratio for a 30 bpp image, according to Rambus. The exact compression ratio achieved can vary based on the content: for visually complex segments, DSC might use a lower compression ratio, whereas, for simpler segments, it can compress more aggressively. Meanwhile, 3:1 is a reasonable compression ratio to expect. With DSC enabled, Samsung's Odyssey Neo G9 theoretically only needs 36.56 Gbit/s, and 48 Gbit/s provided by HDMI 2.1 should suffice.

But it may not be this easy. Before the compression process starts, the uncompressed video frame is first divided into fixed-size segments or slices. One of the configuration parameters in DSC is the slice width. Combined with the total resolution, this parameter will determine how many slices a frame is divided into. While DSC itself is flexible, the implementation of DSC in certain hardware or software might be optimized for popular resolutions, like 1080p, 1440p, and 4K, and may not be optimized for dual 4K. If a particular resolution results in an inconvenient or non-optimal number of slices, it might be less efficient or potentially problematic for certain implementations. The hardware often processes multiple slices in parallel, requiring multiple DSC pipelines. If the number of pipelines is not enough for a particular DSC implementation for a particular resolution, a problem might occur.

For now, we can only speculate why modern GPUs cannot handle Samsung's curved 57-inch Odyssey Neo G9 display properly and whether it can be fixed with software and firmware updates. If QuasarZone's findings are correct, this monitor can only work properly with AMD's latest Radeon RX 7000-series graphics cards.