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.
My conclusion about the PS3's architecture is that while it lacks a shared memory pool or UMA due to the RSX being slapped on late in development, and UMA would have helped.... broooooooo this thing has problems for days
The way every Cell SPE is essentially an island, with its own small memory devs upload executables to, and how they all work on a Ring bus, or Token Ring architecture... just why, Sony? Who even? Most game engines weren't even dual threaded yet, Unreal 3 is not gonna run well on this bro. Bro why tho.