Sony has released details on how end-users should upgrade the storage on their PlayStation 5, as well as some important information on M.2 drive compatibility. There's a bit of fine print to all this that could impact what kind of performance you see if you choose to upgrade your PlayStation 5.
Any SSD being used for PS5 storage needs to support PCI Express 4.0 x4. PCIe 3.0 drives and PCIe 4.0 drives with only an x2 interface are not supported. Supported capacities range from 250GB - 2TB and M.2 2230, 2242, 2260, 2280, and 22110 are all supported. Most PCIe 4.0 drives ship with heatsinks, but if yours didn't you'll need a heatsink for the drive. Sony makes no recommendations beyond noting that one should be installed. Though this should go without saying, SATA drives that fit into M.2 slots are not supported.
At the very bottom of the page(Opens in a new window), at the end of the FAQ section, there's a question PlayStation 5 customers will want to pay attention to:
Do PS5 consoles support Host Memory Buffer? No. Additionally, M.2 SSD devices that support HMB (Host Memory Buffer) may see slower-than-expected performance because the PS5 does not support HMB.
Host Memory Buffer, or HMB, is part of the NVMe 1.2 standard. The highest-performing SSDs typically have a pool of DRAM onboard to store where logical block addresses are physically stored on the SSD. One way to reduce the cost of an SSD drive is to remove this cache and store the data in tables on the SSD itself, but this has a significant impact on performance. HMB offers an intermediate mode.
HMB support allows the SSD to store its memory table inside the system's main DRAM. While this is not as fast as storing the LBA data in dedicated RAM inside the SSD, it's still faster than storing them in NAND. There are plenty of PCIe 3.0 drives that use Host Memory Buffer, including Samsung's 980. We didn't find any PCIe 4.0 devices that also use HMB, but Phison's E19 controller supports it (and it's used, ironically, in the Xbox Series X).
Sony doesn't say that HMB drives won't work, but they're definitely not the preferred option. It's something to keep an eye on if you're trying to source a PCIe 4.0 drive in the months to come. To the best of our knowledge, HMB and onboard DRAM are mutually exclusive -- a drive with integrated RAM has no need for HMB. There may not be many HMB PCIe 4.0 devices out now, but they'll appear in the future as more manufacturers migrate to the standard.
The rest of the upgrade process looks straightforward. Sony includes a guide with images for customers who are leery about opening their console and gives step-by-step instructions on its website. The upgrade is currently in beta testing and Sony notes that PS5 owners who aren't part of its testing program won't see any benefit from installing an M.2 drive right now.
The company also warns that it cannot guarantee identical performance between the secondary SSD and its own internal drive and that performance may not be as good on a user-added drive as on its own native hardware. Combined with the Host Memory Buffer issue, this looks more like Sony warning end-users that the price of broader compatibility is a wider range of potential performance.
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