PCIe 3.0 x8 in PCIe 4.0 x16 [duplicate]

This is for a high bandwidth ssd. I know I can plug the pcie 4.0 card into a pcie 3.0 x16 port directly, but then I would be stuck at the bandwidth of pice 3.0 x16 which wouldn t be able to exploit the full speed of the ssd.

But since I m having pcie 3.0 x24 ports, why not take the additionnal speed offered by x24 over x16 in order to approach the bandwidth of pcie 4.0 x16?
I meaning to get the speed of pcie3.0 x24.
Since it s about using more slower lanes to approach the speed of faster lanes, is it possible?

Of course, I m also thinking about specialized dedicated adapters.

Solution 1:

No, PCI Express doesn't work like that. You can't split one faster PCI-e lane into two slower PCI-e lanes.

It's a bit counter-intuitive, but by combining high lane count, low version PCI-e with low lane count, high version PCI-e gives you worst of both worlds. For example a x16 v2.0 device in a x8 v3.0 motherboard will work at x8 v2.0.

What is possible with PCI-e:

• Running higher version devices on lower version motherboards (downgrades to motherboard version).
• Running lower version devices on higher version motherboards (downgrades to device version).
• Running high lane count devices in low lane count slots (limits throughput to slot's lane count; if the device doesn't fit in the slot you can use a riser or carefully cut off back of the slot).
• Running low lane count devices in high lane count slots (limits throughput to device's lane count).
• If motherboard supports bifurcation, a single x2 or larger slot can be split into two half-slots.

Without bifurcation support, the same can be achieved by using specialized PCI-e switches. To achieve what you want you'd need a "reverse switch", but I haven't heard about such thing yet.