Following his technical breakdown of what we know about the PS4 and what to expect, FXAA creator and programmer Timothy Lottes breaks down what we can expect from Microsoft's Xbox 720 from a very technical standpoint.
Same with the PS4 piece, Lottes is not privy to any behind-the-scenes stuff and is mostly going with what's speculated about the Xbox 720 publicly.
Lottes admits that he's concered with the memory bandwidth of the Xbox 720. Seeing as it's "only" DDR3 for system/GPU memory pared with 32MB of "ESRAM," he deems this "troubling." According to him, 32MB of ESRAM is only really enough to forward shading with MSAA using only 32-bits/pixel color with 2xMSAA at 1080p or 4xMSAA at 720p. Anything else to ESRAM would require tiling and "resolves like on the Xbox360 (which would likely be a DMA copy on 720) or attempting to use the slow DDR3 as a render target." He adds that if this (Xbox 720) GPU is pre-GCN with a serious perfromance gap to the PS4, then the next Xbox will act like a boat anchor "dragging down the min-spec target for cross-platform next-generation games."
His guess is the real reason for the Xbox 720's purported 8GB of memory is because the next-gen console is a DVR which runs "Windows" (which requires 1-3GB of "overhead"), but like Windows RT (Windows on ARM) only exposes on non-desktop UI to the user. Lottes thinks there are a bunch of reasons why Microsoft might ditch real-time console OS implementation, with one of them "being that if they don't provide low level access to developers, that it might enable a faster refresh on backwards compatible hardware."
In theory a developer can target the Xbox 720 like it was a "special DX11 PC" with a few extra changes like hints for surfaces which should go into ESRAM. Then "on the next refresh hardware, all prior games just get better FPS or resolution or AA." Though Lottes notes that if Microsoft does something like this, then it just another PC with lower performance "with all the latency baggage, and lack of low level magic which makes first-party games stand out and sell the platform."
Again, let me stress that same with the PS4's tech specs, these are not carved in stone and in no way confirmed by Microsoft. So, if they're not true, don't blame Lottes for an "inaccurate" report.
Hopefully, rumors that the Xbox 720 will be unveiled in March comes true so we don't have to guess that much in the coming months ahead.
