While Xbox Series X will use proprietary external memory drives to expand its storage space, Sony, opening up in an unprecedented move, is willing to allow users install third-party SSD MVMe drives on its PlayStation 5.
This is what PS5 official specs show, but also what Mark Cerny has explained in detail during the system architect's "The Road to PS5" presentation a moment ago, mentioning both PlayStation 5's compatibility with other manufacturers' memory solutions and certain requirements for storage solutions to be approved.
Solid state storage included with every PS5 is able to transfer data at a speed of 5.5 GB/s. Nowadays, there's no SSD drive in the market reaching those speeds, but Cerny and his team expect the technology to follow PCIe 4.0 steps (which currently is at 7.0 GB/s) in the following months so that solid memories reach and surpass PS5's launch SSD speed. In fact, this is a requirement.
Effectively, any SSD NVMe memory willing to be officially supported by PS5 must transfer at 5.5 GB/s at the very least, but what is more, it'll have to pass Sony's own compatibility testing process so as to obtain its official certification. Cerny points out there are drives of different sizes and shapes that could perhaps not fit in the hardware or some that even sport their own cooling system. Sony is already testing different drives ahead of PS5 final release.
This approach might theoretically provide a significantly faster solution in the long run but, naturally, even though third-party competition could bring retail prices down, the requirements in terms of both minimum speed and official certification could cause the cost of expanded storage to rise during the next-gen console's first months in the market.