When the PS4 Pro was revealed, it was mentioned that it would have retained the original PS4 configuration with 8 GB of GDDR5 RAM, albeit with higher bandwidth, but that's not entirely correct, as revealed by System Architect Mark Cerny today in an interview on Eurogamer.

On top of the cutting-edge GDDR5 RAM, the console will also include one additional gigabyte of slower DDR3 RAM, which will open up a few possibilities.

"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 [...] 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."

"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."

Cerny also clarified that developers can use the additional RAM as they see fit. It's certainly not an enormous boost, but every little bit helps.