This video shows the kind of frame rate improvement beta users are already seeing with the PS4 Pro's Boost Mode.
Thus far, to get a benefit from the extra hardware inside the PS4 Pro, developers have had to code game-specific patches to activate features like higher resolutions, smoother frame rates, or increased detail on in-game objects. Now, there are signs Sony is planning to add an optional "Boost Mode" that could smooth out the frame rate on some older titles without the need for any specially coded patches.
While the Boost Mode was not mentioned in today's official announcement of the coming Version 4.5 of the PS4 firmware (which also adds external hard drive support), reports of its existence are starting to leak out from users who are signed up for the beta version, which launched today. In a NeoGAF thread, a few posters have uploaded separate screenshots, apparently from the beta, describing the Boost Mode in both Japanese and English.
The English description for the mode reads:
from New PS4 Pro “Boost Mode” could improve even unmodified titles