CUPERTINO, Calif. — Microsoft described Scorpio, the SoC inside its Xbox X One. The device, detailed at Hot Chips, aims to balance cost and performance for 4K gaming in a console shipping in November.
Scorpio packs 7 billion transistors with 6 TFlops graphics performance in a 359 mm2 chip made in a 16FF+ TSMC process. The chip, designed in partnership with AMD, also packs eight x86 cores running at 2.3 GHz and sharing 4 Mbytes L2 cache.
Scorpio uses 12 GBytes of GDDR5 memory rather than 32 MBytes embedded SRAM used in a prior generation or a high-bandwidth memory (HBM) module which engineers considered. “We were a little nervous making a consumer product with data moving around at 6.8 GHz,” said John Sell, a Microsoft distinguished engineer, referring to the GDDR5 data rate.
The single large block of memory enables much simpler tools for application developers, Sell said. It also emulates the embedded SRAM for compatibility with apps written for the prior console.
Microsoft kicked the tires of the kinds of HBM modules AMD pioneered in GPUs in 2015 and Nvidia uses now on Volta. “But for a consumer product HBM2 is too expensive and inflexible…its memory bandwidth is not as granular, and we would be locked into [an HBM] module,” Sell said.
It’s too early to tell what the next generation trade-offs will look like, but both a Jedec GDDR6 and an HBM3 are in the works. A major cost issue for HBM is a lack of test coverage and thus relatively low yields, he said.
Next page: Diagram of chip and demo of console
Graphics (yellow) make up the brunt of Scorpio. (Image: Microsoft)