Steam Machine can output 4K at 120Hz, but with a significant sacrifice

Valve has unveiled the Steam Machine, a new PC gaming and console hybrid device that is expected to be released early next year. Valve says the console is targeting 4K at 60FPS, but we have learned that it is capable of 4K at 120Hz over HDMI, albeit with some pretty big sacrifices.

Valve has marketed the Steam Machine as a device targeting 4K 60FPS, but diving into the specifications and reports surrounding the upcoming hybrid device we have learned the Steam Machine is actually capable of 4K 120Hz, whether it will actually hit 4K at 120FPS in mainstream games is another thing entirely, but at least when it comes to output, it is capable of 4K 120Hz.

Firstly, the Steam Machine comes with DisplayPort 1.4, which is capable of up to 4K 240Hz / 8K 60Hz. The Steam Machine plugged into a 4K 240Hz monitor will output at 4K 240Hz, but TVs don't have DisplayPort connectivity; they use HDMI ports. One of the biggest glaring issues with the Steam Machine is the HDMI being limited to the 2.0 specification, which means it's limited to 4K 60Hz output. This is particularly annoying considering the hardware within the Steam Machine, an AMD RDNA 3 GPU, is technically capable of 4K 120Hz output, and many modern TVs are now capable of 120Hz over HDMI 2.1.

However, Oliver MacKenzie from Digital Foundry has reported that while he was at Valve HQ testing out the Steam Machine, Valve engineers stressed to him that the Steam Machine is capable of 4K 120Hz. Technically speaking, 4K 120Hz is possible over HDMI 2.0, but you still have to work within the 18 Gbps bandwidth limitations of the specification, meaning sacrifices have to be made in order to reach 4K 120Hz over the 2.0 spec.

For example, HDMI 2.0 can push 4K at 120Hz by cutting the color bandwidth in half, meaning the display the device is plugged into must accept 4K 120Hz 4:2:0 (most modern LG/Samsung 4K TVs do). By reducing the color bandwidth, you will be significantly reducing the color quality and locking the output to SDR only, meaning no HDR content.

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So, technically, you can put 4K 120Hz on the Steam Machine over HDMI, but whether or not you actually want to do that is another thing entirely, as the image quality hit may not make the increase in refresh rate worth it at all. It seems that 4K 120Hz will be mostly reserved for dedicated gaming monitors and other displays that can take advantage of the DisplayPort connectivity.