Sorry for this kinda gamerbrained question.
The Xbox 360, Playstation 4, Xbox One, honestly most consoles after the Playstation and Saturn have shared memory pools. It allows flexibility in how much memory and VRAM developers want to assign, right? Why does the PS3 not have a shared 512MB pool of GDDR3? It caused all kinds of problems, most notably with Bethesda games.
Is it the Cell Broadband Engine needing the specialty XDR memory? Is it an artifact of the Nvidia RSX graphics chip being added late in development? Looking back I a)most wonder if the split memory was more of a problem than the Cell tbh.
I can only guess as to what is going though Sony executives’ heads sometimes. Though the ps3 did it’s most important job (to sony) extremely well: pushing the Blu-Ray to be the dominant format for HD home video.
For all the good it did them winning that war, when Netflix was popular by 2010