It has 1 GB slower RAM for non-critical apps additionally to the 8 GB GDDR5 RAM of the other PS4-models:
"We felt games needed a little more memory - about 10 per cent more - so we added a gigabyte of slow, conventional DRAM to the console," Cerny reveals, confirming that it's DDR3 in nature. "On a standard model, if you're switching between an application, such as Netflix, and a game, Netflix is still in system memory even when you're playing the game. We use that architecture because it allows for a very quick swap between applications. Nothing needs to be loaded, it's already in memory."
Some might say it's an extravagant use of the PS4's fast GDDR5 memory, so the extra DDR3 memory in the Pro is used to store non-critical apps, opening up more RAM for game developers.
"On PS4 Pro, we do things differently, when you stop using Netflix, we move it to the slow, conventional gigabyte of DRAM. Using that strategy frees up almost one gigabyte of the eight gigabytes of GDDR5. We use 512MB of that freed up space for games, which is to say that games can use 5.5GB instead of the five and we use most of the rest to make the PS4 Pro interface - meaning what you see when you hit the PS button - at 4K rather than the 1080p it is today."
