It has 1 GB slower RAM for non-critical apps additionally to the 8 GB GDDR5 RAM of the other PS4-models:

http://www.eurogamer.net/articles/digitalfoundry-2016-inside-playstation-4-pro-how-sony-made-a-4k-games-machine

"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."

Thats quite neat!

Thats... pretty smart.
More GDDR5 for gameing instead.

Mark Cerny and those hardware design guys at Sony do good work / smart choices.

Excellent news. Even more powerful than I first thought. for $399 this a steal.

Yup. There were a few other interesting bits in there:

1) why they chose to stick with the same CPU and similar gpu set up. The whole thing where Cerny said they built it like a mirror. He said he tested changing CPU and GPU set ups and it would create bugs and other problems. This meant that the games which are already out may have issues and it wasn't worth the risk.

2) In other words, at full floats, we have 4.2 teraflops. With half-floats, it's now double that, which is to say, 8.4 teraflops in 16-bit computation. This has the potential to radically increase performance."

Not sure what half floating points are, but it looks like theoretically, 4.2TF is the base.

It's not "full floats" it's "Single Precision". - You also have "Double Precision" and of course "Half Precision" that you state.
It's basically a limit on how accurate/complex the floating point can get.

But this is rehashing old stuff that I have already gone over in other threads, but Half Precision/16-bit floating point isn't a game changer.

Indeed. This was a smart choice, could have been taken a step farther, but I digress.
It should bring some good benefits for minimal cost.