According to a report by HardwareLuxx, Valve has made a spec change to the Steam Deck's SSD specs on May 28 that has largely flown under the radar. The change allows the use of two drive configurations instead of just one, cutting the potential SSD bandwidth in half for some models. As a result, the PCIe Gen 3 NVMe drive built into the higher-end models will now come with access to either four PCIe lanes (x4) or two lanes (x2). However, customers won't know which drives they'll receive, with the company noting that, "Some 256GB and 512GB models will ship with a PCIe Gen 3 x2 SSD."
Valve says that it tested the change and it will not affect gaming performance. Here's Valve's description of the change:
"256 GB NVMe SSD (PCIe Gen 3 x4 or PCIe Gen 3 x2*)
512 GB high-speed NVMe SSD (PCIe Gen 3 x4 or PCIe Gen 3 x2*)
*Some 256GB and 512GB models ship with a PCIe Gen 3 x2 SSD. In our testing, we did not see any impact to gaming performance between x2 and x4."
Valve doesn't say why it made the change, but there are still a number of NVMe SSDs on the market that only support two PCIe Gen 3 lanes. In fairness, SSDs of this caliber are still very capable drives, and much faster than SSDs with the SATA 3 interface. With a two-lane SSD running at Gen 3 speeds, you can still receive up to 2048 MB/s of bandwidth, which is four times greater than SATA SSDs. However, that's half the theoretical peak of the x4 connection found in some models. As a reminder, only a handful of games made today can utilize the full storage bandwidth of an SSD. For more details on SSDs, check out our Best SSDs article.
The 256GB and 512GB NVMe models are the only models receiving this change. The baseline 64GB model will stay the same with its much slower eMMC drive running on a PCIe Gen 2 x1 configuration. There is also no option to choose, or know, which type of drive you'll receive — it appears to be a bit of a lottery. We're reaching out to Valve for more detail.
Valve also confirmed that the spec changes are only for the NVMe drives, while the high-speed MicroSD slot will remain identical between all three variants. The company recently announced that it is doubling its production every week, so you can expect to see a lot more of the devices in the wild soon.