Back in March, Microsoft announced what it was calling the “Xbox Velocity Architecture” for the Xbox Series X, and we got excited about the prospect of data streamed from long-term storage at advertised rates up to 4.8GB/s (compared to just 68MB/s on the Xbox One). Today, Microsoft offered some new details about how, exactly, the company got such high speeds from the hardware’s I/O systems.
The bulk of the speed increase, as Microsoft has said before, comes from the system’s use of NVMe SSD memory, rather than the much slower-spinning hard drives of past consoles. That gives the system “2.4 GB/s of raw I/O throughput,” Microsoft says, though we’ve noted previously it will also likely make expanding that memory past the built-in 1TB default more expensive.
To extend that speed even further, Microsoft says it’s expanding on the “industry standard LZ decompressor” with “a brand new, proprietary algorithm specifically designed for texture data named BCPack.” This hardware-accelerated texture-unpacking algorithm can be run in parallel with the standard LZ decompressor, Microsoft says, increasing the functional throughput of the I/O bus without using up precious CPU core cycles. In fact, without hardware acceleration, Microsoft says similar software-exclusive decompression methods “would require more than four Zen 2 CPU cores” to achieve the same results.