The PlayStation 5 SSD comes in an odd capacity and can fill 16 GB of RAM in just two seconds
It was clear from the very beginning that both the Xbox Series X and the PlayStation 5 will switch to SSDs from HDDs to speed up game load times. While the Xbox Series X's drive was already fast enough with the option an equally fast external storage, Sony is taking a different approach.
The PS5's 825 GB internal SSD connects to a custom flash via a 12-channel interface delivering 5.5 GB/s of raw throughput. The odd storage capacity allows Sony to make good use of available NAND while having the freedom to play around with its interface thereby, alleviating the need to stick to conventional M.2 design and minimizing costs. The PS5's SSD is so fast that the console's 16 GB of memory can be filled in just two seconds (2 GB in 0.25 seconds).
The controller connects to the CPU via a four-lane PCIe Gen4 bus and is custom built so that developers can prioritize data blocks to eliminate any bottlenecks. The controller uses a hardware decompressor that has a performance equivalent to nine Zen 2 cores. It supports decompression of the Kraken format developed by RAD Game Tools, which ultimately translates to a throughput of up to 9 GB/s.
Also in the offing is a dedicated DMA controller equivalent to the performance of one or two Zen 2 cores, custom processors that handle the I/O mapping, and coherency engines. Developers need not fret about utilizing the full capabilities of the storage subsystem as the PS5 handles everything invisibly.
Things are a bit different when it comes to external storage, though. Traditional external hard drives can be used for storing backward compatible PS4 titles. Unlike Microsoft's implementation, even PC NVMe drives can be used. The important criteria here is not the nature of the flash used on the external M.2 itself but its interface — ideally, you'd want it to be a PCIe Gen4 drive.
That being said, the PS5's storage is way ahead of anything that's on offer from the PC side. It has six priority levels while PC NVMe drives right now have only two. Cerny suggests waiting before purchasing an external NVMe drive to ensure it passes Sony's validation for fitting inside the slot and bandwidth requirements.
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