A listing for Samsung’s upcoming 990 Evo SSD has appeared online. Though the release of a 990 Evo series SSD is not at all unexpected, its PCIe lane configuration is surprising, and it’s an interesting configuration at that.
The 990 Evo listing popped up on Samsung’s Ukraine website (spotted by WinFuture). It reveals the drive supports both PCIe 4.0 x4 and PCIe 5.0 x2 connections. The specifications show the drive will support 5000MB/s and 4200MB/s read and write speeds respectively. Compared to the best SSDs, that’s nothing special, and well within the capabilities of a PCIe 4.0 x4 connection, but it’s the 990 Evo’s hybrid PCIe 5.0 x2 support that got my attention.
Of course, there’s nothing stopping you from using a PCIe 4.0 x4 drive in a PCIe 5.0 x4 slot, but doing so means the drive uses up four PCIe 5.0 lanes—a waste of valuable lanes. In the 990 Evo’s case, PCIe 5.0 x2 support won’t hurt performance, but it opens up some flexibility potential. I don’t see any benefits for mainstream users at this time due to current chipset configurations, lane implementations and a lack of laptop PCIe 5.0 support, but in the future, I believe this dual support flexibility is a smart thing.
Future chipset derived lanes will move from Gen 4 to Gen 5 at some point, but motherboards already face cooling and electrical challenges with Gen 4 drives—not to mention their steep cost. Boards with a full set of Gen 5 slots will cost even more than they do now.
There are two probable stumbling blocks to x2 M.2 SSD adoption, one of which is motherboard support. Motherboard manufacturers would consider hard-wired x2 slots as limiting performance. OK. How about some proper bifurcation support then? A board supporting a single PCIe 5.0 x4 drive from the CPU plus another pair of chipset derived PCIe 5.0 x4 slots (or four x2 slots) is hardly going to be limiting to mainstream users. And if it is, there are add-in cards or workstation solutions.
The second barrier is how SSDs are promoted. As long as the big sticker on the front of the SSD package highlights sequential read and write speeds, high performance drives are likely to stick with an x4 configuration. Of course, there’s more to an SSD than sequential transfers. The IOPS, random and internal transfer performance of a drive are just as important, and that should not be any different on a like-for-like PCIe 4.0 x4 drive compared to a PCIe 5.0 x2 one. Will the average buyer understand that though?
Give me a single CPU connected high performance PCIe 5.0 x4 drive and 2 or 3 slower, but still plenty fast x2 drives for secondary storage on a cheaper motherboard and I’d be very happy. On the laptop side, an x2 drive will save a bit of power here and there, which can’t hurt battery life, while lowering temperatures a little.
We can probably expect to hear more about the Samsung 990 Evo at CES. I hope it’s just one of many PCIe 5.0 x2 drives.
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