Digital Foundry received an Xbox Project Scorpio whitepaper from an anonymous source, although they were able to validate its authenticity. Basically, they sent it to their own, off-the-record sources who would have access to the same info, and those individuals confirmed it’s an official document that they’ve seen before. Of course, the trust bottlenecks through Digital Foundry, but they’re about as reputable as you can get in this industry, so that works.
Anywho, disclaimer aside, the whitepaper unveils a few interesting details about how Project Scorpio is expecting to provide higher performance. The most interesting change is what’s missing: the small, on-chip RAM (ESRAM). Microsoft claims that the higher global memory bandwidth removes the need to have it on Project Scorpio.
Digital Foundry is still a bit concerned that, while the 320 GB/s bandwidth might be enough, the latency might be a concern for compatibility. Personally, I’m not too concerned. Modern GPUs do a huge amount of latency-hiding tricks, such as parking whole shaders at global memory accesses and running other tasks while the GPU fetches the memory the original shader needs, swapping it back and finishing when it arrives. Also, the increased GPU performance will mean that the game has more room to be wasteful of GPU resources, since it only needs to perform at least as good as a regular Xbox One. I expect that there wouldn’t be enough round-trips to ESRAM for it to be a major slowdown when running on Project Scorpio (and its not-ESRAM).
Seriously, Wall-E with a Freddie Mercury 'stache.
Microsoft does suggest that developers make use of ESRAM on Xbox One and Xbox One S, though. Yes, don’t deliberately throw away performance on the slower machines just because that accelerator isn’t available on higher-end devices, like Project Scorpio or a gaming PC (heh heh heh).
Another point that Digital Foundry highlighted was that the actual number of rendered fragments (pixels that may or may not make it to screen) didn’t scale up by a factor-of-four (going from 1080p to 4K) in all cases. A first-party developer noticed a case where it was only a 3.5x scaling between the two resolutions. (This metric was actually rendered pixels, not even just GPU load, which would include resolution-independent tasks, like physics simulations.) I’m not exactly sure how the number of fragments decreased, but it could be due to some rendering tricks, like when Halo renders the background at a lower resolution. (Yes, I’m using Khronos verbiage; it’s less ambiguous.)
They also assume that Project Scorpio will use pre-Zen AMD CPU cores. I agree. It seems like Zen wouldn’t be around early enough to make production, especially when you consider the pre-release units that are circulating around Microsoft, and probably third-party developers, too.
Project Scorpio launches this holiday season (2017).