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I am doing a supper-budget-ghetto computer project. Just wanted to ask a theoretical question: could spliced up risers be used to turn one 1x and one 16x slot to two 8x slots? I think they share a common bus soo...?

I know that I could do necessary tinkering and soldering, just wanted to ask you guys before I spend some money on actual risers and cut them to pieces :)

I've found similar question (Can i run several links through single pcie x8 connector?), last comment to accepted answer looks promising but I wanted to make it more specific

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    \$\begingroup\$ I'm not sure this is an electronic design question. \$\endgroup\$
    – Bort
    Commented Jan 29, 2018 at 21:09
  • \$\begingroup\$ I wasn't sure neither so, please, if you know a forum better suitable for this question I will move my question there. The problem is I did some digging and this is the best place I can think of... \$\endgroup\$
    – Milut
    Commented Jan 29, 2018 at 22:25
  • \$\begingroup\$ Well, is this a computer question, or an electronic design question? (Are you asking if X is compatible with computers, or if X design will work as a circuit?) \$\endgroup\$
    – Bort
    Commented Jan 29, 2018 at 22:54
  • \$\begingroup\$ Totally from electrical point of view. I know that hardware compatibility can be tricky and such design (if plausible) might as well not work in some computers. Im not asking if it is going to work in a given PC, just if it is theoretically plausible. \$\endgroup\$
    – Milut
    Commented Jan 29, 2018 at 23:26
  • \$\begingroup\$ related to electronics.stackexchange.com/q/324646/16935 \$\endgroup\$
    – Alex P.
    Commented Feb 19, 2018 at 20:27

2 Answers 2

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The best you could hope to do is bifurcate the x16 slot into two x8 slots. This will require support from the upstream device (CPU or PCIe switch). If it's supported, then I believe this would be implemented by changing how the configuration registers are set, which is likely done in BIOS before the machine boots so the PCIe bus is properly enumerated. So yes, it is possibly doable, but it would depend on the motherboard design and would require editing the BIOS. And you would also need to buffer the reference clock.

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One 16x-lane PCIe port can be split into two 8x-lane PCIe. It's called PCI Express Slot Bifurcation.

If your board does not support PCIe slot configuration in BIOS - you could just hard wire the CFG5 and CFG6 pins in the CPU socket.

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    \$\begingroup\$ Your link is no good, which is why you should copy and paste the important details as part of your answer. Without the diagrams, there is no way to find the CFG5 and CFG6 pins. \$\endgroup\$
    – user105652
    Commented Feb 19, 2018 at 19:57

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