When Sony’s upgraded Playstation 4 Pro shipped it only offered performance improvements for games that were updated to support it. That’s a manual process that costs money (in wages) on the part of the developer to support. Not every game is going to get an update. It’s an impossible task for games that have had their development teams disbanded, or small studios that don’t have time to go back and retest and resubmit their updates to Sony.
An upcoming firmware update (4.50) is to resolve this issue, partially. Boost mode will offer enhanced performance for all older games. With the caveat that there is no guarantee they will support it.
In short, boost mode will work best in stabilising performance closer to target frame-rates and should prove interesting on unlocked titles, but you can’t expect game-changing miracles. Games like Destiny that stick doggedly to their 30fps cap will see no improvement, and titles certainly won’t break their performance limits and suddenly run at 60fps. However, there are plenty of games out there that glitch badly or run nowhere near their theoretical limits. In this scenario, boost mode could be revelatory.
Enhanced performance isn’t everything, and I’d be surprised if Sony didn’t eventually blacklist games that don’t work well with the boost, but this is huge news for anyone that bought a Pro and a disappointment for anyone that bought the regular Playstation 4 before this functionality was announced.