[wtallis]

These processors will use the existing AM5 socket, so they fundamentally cannot make major changes to lane counts and allocations, only per-lane speeds. They're also re-using CPU's IO die from last generation and re-using the same chipset silicon, which further constrains them to only minor tweaks.

Typical use cases and motherboards give an x16 slot for graphics, x4 each to at least one or two M.2 slots for SSDs, and x4 to the chipset. Last generation and this generation, AMD's high-end chipset is actually two chipsets daisy-chained, since they're really not much more than PCIe fan-out switches plus USB and SATA HBAs.

Nobody allocates a single PCIe lane to an SSD slot, and the link between the CPU and chipset must have a lane width that is a power of two; a seven-lane link is not possible with standard PCIe.

Also, keep in mind that PCIe is packet-switched, so even though on paper the chipset is over-subscribed with downstream ports that add up to more bandwidth than the uplink to the CPU provides, it won't be a bottleneck unless you have an unusual hardware configuration and workload that actually tries to use too much IO bandwidth with the wrong set of peripherals simultaneously.

[dhx]

Thanks for the description. The article was confusing as to whether the CPU's stated 24x PCIe 5.0 lanes included those required for the chipset. Given that the same AM5 socket is used and X870E is similar to the X670E, this appears to not be the case, and instead the 9950X would have 28x PCIe 5.0 lanes, 4 of which are connected to the daisy-chained chipset and 24 then remain available to the motherboard vendor (nominally as 16 for graphics, 8 for NVMe). I also hadn't realised the CPU would offer 4x USB 4.0 ports directly.

Block diagram for AM5 (X670E/X670): https://www.techpowerup.com/review/amd-ryzen-9-7950x/images/...

Block diagram for AM4 (X570): https://www.reddit.com/r/Amd/comments/bus60i/amd_x570_detail...

[adrian_b]

Cheap small computers with Intel Alder Lake N CPUs, like Intel N100, allocate frequently a single PCIe lane for each SSD slot.

However you are right that such a choice is very unlikely for computers using AMD CPUs or Intel Core CPUs.

[adgjlsfhk1]

with pcie 5, 2x is almost certainly enough for all but the absolute fastest drives.