Alrighty then, I will mention bitness.
I apologize for the curtness. Please understand, very few people enjoy being told what they were thinking.
Earlier was an attempt at being brief on the convenience of memory size. But a longer post is needed.
The motivation for my mentioning increasing memory space has to do with developer convenience. (John Carmack interviews.)
However that is a greedy request, adding more cost to a system that already offers more bandwidth and storage than we are using.
The same as crying for lower priced all-you-can-eat buffets, when all you are eating is the snow crab, and not trying something new.
On the Xbox360 if you reduce the native resolution you lower processing demand placed on Xenon/Xenus and allow more space for logic.
It is honestly that simple. And because it is easy to do this, many developers have lead with easy.
On the PS3 if you lower the resolution you free up more GDDR3 memory.
Yet the Cell can handle a lot more Geometry & Shader processes than Xenon. So why focus on reducing processing load by doing smaller GDDR3 resolutions?
Additionally, the PS3 was not designed for Cell's cores rely on making direct requests from the GDDR3 memory.
So to do this, you might create a very small buffer pool in the XDR space to stream from GDDR3 to XDR to Cell cores.
Even though once you have done this, it is easy to do again, cell shader calls could be set up to automatically initiate the process.
With dedicated/pre-partitioned memory you have the advantages of both higher bandwidth and lower memory latency.
But you have the disadvantage of managing two separate pools and one storage space limit (XDR) to make calls from.
{256MB of GDDR3 is more than generous enough to be equal to the graphical needs of all in game action on the Xbox360. It's target resolution promised no games below 720p. That was even part of its official FAQ. Yet as mentioned smaller resolution makes processing easier. So games like Halo3 (640p) wind up being less than 720p.}
A better and smarter approach than wishing for additional XDR Memory
When developing cross platform games leading on the PS3 it is easier to work around slowness on Xbox360 by making games smaller.
Because when you come over from the PS3 you have more speed, more storage, though DRAM is divided in its physical space.
So why not use the unified space on Xbox360 as a single collecting pool for, PS3 lead cross platform developing?
It would be a lot easier to reduce texture sizes, frame rate, or size, while moving two separate memory pools into one.
The decision to lead with the Playstation3 makes a lot of sense when you reverse the picture.
If you start with the PS3 then you don’t have to get creative to overcome having divided memory or programming.
Because all the divisions you make can be combined into a single pool on the Xbox360.
Then IF your game is limited by reduced memory and processing speed you can simply shrink it down on the Xbox360.
Problem solved. It is easier to down sample a few factors (Xbox360), than it is to grow into a separated parallel shape (PS3).
