Sony has made a big deal about how the PS4 Pro is an iteration not a replacement for current hardware. Things might look prettier, and frame rates might be faster, but otherwise a Pro is still just a PS4. That means it has to play old games and only take advantage of extra features when called upon.

To do this, games that support the new console will have a ‘base’ and a ‘pro’ mode depending on the hardware they’re played on, and the ability to switch between the two comes from actually doubling existing hardware.

Speaking to Eurogamer, PS4 architect and really clever person Mark Cerny explains how the GPU (graphics processor unit) is repeated in the PS4 Pro. “We doubled the GPU size by essentially placing it next to a mirrored version of itself. That gives us an extremely clean way to support the existing 700 [PS4] titles. We just turn off half the GPU and run it at something quite close to the original GPU."

But, stick a Pro game, in and both chips are activated, doubling the GPU’s power while the CPU runs at the same rate - something Cerny says is important to ensure compatibility with older games.

There’s also a little extra RAM in the PS4 Pro via 1GB of DDR3 (the PS4 and Pro already has 8GB of faster GDDR5). "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,” explains Cerny. “It allows for a very quick swap between applications. Nothing needs to be loaded, it's already in memory.” Now, when you do something similar on the PS4 Pro it uses the slower extra 1GB, leaving the faster GDDR5 RAM free.

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