One of the problems the PS4 Pro faced prior to launch was the fact that people didn't fully understand what benefit they'd get out of the PS4 Pro if they were just playing on a regular screen, with their regular games.
Boost Mode helps answer that question. It's an option in an upcoming firmware patch that will let older games take advantage of the PS4 Pro's newer hardware. But exactly how much of a benefit do you get?
Digital Foundry put a PS4 Pro with a latest version of the firmware through its paces. They used games like Battlefield 4, Mirror's Edge Catalyst and Tomb Raider: Definitive Edition, games that haven't received a PS4 Pro-specific patch.
In pretty much every case, Boost Mode resulted in higher frame rates, smoother gameplay, and in some instances faster texture streaming. Boost Mode can't fix everything though: the PS4 port of Broforce still runs like arse.
Given that Microsoft is in a similar position where all games for Project Scorpio also have to run on the Xbox One, I wouldn't be surprised if they come out with a Boost Mode of their own. We'll also keep you posted as to when Boost Mode becomes available to all PS4 Pro owners.