The PS4 has a super fast memory architecture in GDDR5 which is capable of 176GB/s bandwidth, however, Mark Cenry has mentioned that they had thought about an alternative memory architecture.
As you can see in the above image on the right, one of the so called memory architecture they had thought of was going with was GDDR5 memory with 88GB/s bandwidth which is slower than the one they finally went with, along with a small amount of eDRAM which provides a bandwidth of over 1000GB/s. That sounds great doesn’t it? But Cerny said that it would have been difficult to code for it in a straightforward way and developers had to come up with a separate technique to take full advantage of it.
The Xbox One features a small amount of eSRAM and offers the same functionality of high bandwidth to make up for the slow DDR3 RAM.
That’s the main reason Sony chose the memory architecture on the left of the image. The high bus and a unified memory at a 176GB/s would have made it really easy for developers to code for and it was their philosophy to provide a simple architecture with the PS4. Cerny said that the 256-bit bus GDDR5 bandwidth at 176GB/s ”is quite a lot”.
He revealed that the third-parties had demanded a unified memory architecture with a powerful GPU. This is in complete contrast with the PS3 which had a fairly weak GPU in the RSX and a divided XDR memory. Sony had originally planned to go with just 4GB GDDR5 but certain third-party developers managed to convince them that it was a really bad idea.
He revealed this information at GameLab presentation in Barcelona which has just concluded now. However, you can catch up on it here.