Microsoft has a way with words, their marketing team is strong. It looks like most Xbox only fans seem to be buying into the 12GB/s narrative, even though that is NOT what Microsoft said (but worded to purposely mislead). This information is from
https://news.xbox.com/en-us/2020/07/14/a-closer-look-at-xbox-velocity-architecture/.
First, let's look into the actual I/O performance. There will be omissions as I don't want to copy the whole text, but please check the original article as I want to keep the context intact:
Custom NVME SSD
Translation: As opposed to normal PC SSD's, this one is designed to deliver consistent
2.4 GB/s raw I/O throughput. That's it. That's as much as you're gonna get.
Hardware Accelerated Decompression
Translation: If you assume a 2:1 compression ration, which is perfectly possible, you will get a 4.8 GB/s compressed I/O throughput. I will assume this is on average, so the peaks will likely be higher, up to whatever their decompressor allows, and some data will not compress as well, but that's it. Your average is 4.8 GB/s, not more, not less.
Sampler Feedback Streaming (SFS)
Translation: First, let's clarify again - The Series X still has a
raw I/O throughput of 2.4 GB/s. Now that we've clarified that, let's clarify the funny word play. Assuming the numbers they mentioned are correct, on older systems you'd access 1/3 or less of the loaded textures, and with the new tech,
you boost utilization by 2.5 of the effective raw bandwidth. This means that if you didn't have this tech, your available bandwith would be equivalent to 0.96 GB/s, as you'd be loading that data you don't need. This is pretty much what we saw with their old gen game switching (video below), where the average time to switch between game A and B was of 6 seconds, or 5.76 GB/s of RAM being loaded (games were programmed for 5.5 GB/s AFAIK).
So, to recap, the capabilities are:
- 2.4 GB/s raw I/O throughput
- 4.8 GB/s compressed I/O throughput.
- A boost of 2.5 times compared to old gen tech, meaning you can fully utilize the numbers above, as opposed to 1/3 of the numbers available to last gen games
Also, I'm not devaluing the tech. This is great, because without SFS, they would be loading 10 or 13.5GB into RAM only to actually need 1/3 of that. This gives Devs way more usable space which, coupled with the super fast SSD speeds, will effectively provide a generational leap.
Edit: Sorry, forgot the video I mentioned above