In addition to a new Siri Remote and a faster A12 processor, the refreshed Apple TV 4K that Apple announced today has a number of other notable hardware improvements.
The new Apple TV 4K is equipped with an HDMI 2.1 port instead of an HDMI 2.0a port, and it offers support for 4K 60 fps HDR video output. Code recently found in tvOS 14.5 suggested the new Apple TV could support 4K 120Hz output, but that does not appear to be the case.
Along with HDMI 2.1, the new Apple TV supports 802.11ax WiFi 6 with MIMO. Apple has been introducing WiFi 6 support in its newest devices, and WiFi 6 is the newest and fastest WiFi protocol available with improved speeds, expanded network capacity, lower latency, better power efficiency, and upgraded performance in locations with many smart home devices.
The Apple TV 4K is the second Apple device that has built-in Thread support, following the HomePod mini. Thread is a low-power networking technology that offers a secure, mesh-based system able to interface with other Thread-enabled smart home devices for improved connectivity.
Though not mentioned in the Apple TV specifications, the tvOS 14.5 beta suggests that the new Apple TV model supports eARC, which offers a bandwidth and speed boost for sending higher-quality audio from the TV to a soundbar or receiver.