Most notable feature for me: Boost mode (applicable to PlayStation 4 Pro only)
PS4 Pro gets a new feature in this update called Boost Mode. This feature has been designed to provide better performance for legacy titles that have not been patched to take advantage of the PS4 Pro’s faster CPU and its faster and double-sized GPU. This can provide a noticeable frame rate boost to some games with variable frame rates, and can provide frame rate stability for games that are programmed to run at 30 Hz or 60 Hz.
Depending on the game, the increased CPU speed may also result in shorter load times. Keep in mind that Boost Mode is not guaranteed to work with all titles. Turning the setting off will allow the game to be played in a mode that replicates the standard PS4.
You can turn on the Boost Mode from the PS4’s Settings menu. Go to ‘Settings’, then ‘System’, then scroll down to ‘Boost Mode’ and tick the box to turn Boost Mode on.