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PCIe bifurcation is a function of what your CPU and/or PCH can do. There are hard limits in the silicon as to how you can divvy up your lanes.
by c_o_n_v_e_x 4y ago
PCIe bifurcation is a function of what your CPU and/or PCH can do. There are hard limits in the silicon as to how you can divvy up your lanes.
- fomine3 4y agoSplitting CPU lane to x8/x8 is supported at least. Just mobo manufacturers don't want to implement it as a dedicated slot. It seems that Alder Lake no longer support x8/x4/x4 sadly.
- wtallis 4y ago> It seems that Alder Lake no longer support x8/x4/x4 sadly. I would be very surprised if the silicon doesn't still support 8+4+4 operation. I suspect the lack of available motherboards with this config comes down to the expense of getting a PCIe gen5 signal to reach the third slot. It may require both the extra mux and a redriver or retimer.
- fomine3 4y agoI found this from quick Googling https://forum-en.msi.com/index.php?threads/does-pro-z690-a-and-mag-z690-tomahawks-pcie-5-0-x16-slots-support-pcie-bifurcation.375664/ https://forum-en.msi.com/index.php?threads/does-pro-z690-a-a... Perhaps why they dropped the support is because the reason you wrote? Still I wonder is it possible to have Gen5 x8 and Gen3 x4/x4.
- eigen 4y ago> It seems that Alder Lake no longer support x8/x4/x4 sadly. Sort of. support is "Up to 1x16+4, 2x8+4" [1] so could be used as x8/x4/x4, the remaining 4 lanes are unused in the x8, as there are 20 PCIe lanes on the CPU. [1] https://ark.intel.com/content/www/us/en/ark/products/228441/intel-core-i912900hx-processor-30m-cache-up-to-5-00-ghz.html https://ark.intel.com/content/www/us/en/ark/products/228441/...
- fomine3 4y agoAh yes, but everyone (and every manufacturer) want to use +x4 port for M.2 SSD so not usable for other PCIe devices.