Does bifurcation have to be fully populated?

hi all

if i bifurcate an x8 into x4x4 or x16 into x4x4x4x4 for the purposes of an m.2 carrier card, do i need to have all m.2 slots populated or can i leave any combination of them empty?

the answer is harder to find

It should be fine to leave a few of them empty; bifurcation is just a way to split lanes into more ports.

Worst case in case you cannot:

One NVMe drive - don’t bifurcate
Two NVMe drives - do an x8 / x8
Three NVMe drives - do x4 / x4 / x8
Four NVMe drives - go full x4 / x4 / x4 / x4

So buy and try, I guess?

understood, cheers

the actual use case is that i’m planning an epyc h11ssl-i build and if i can dedicate a x8 or an x16 slot to a carrier card and it doesn’t matter how many m.2 cards are populated i’ll use a 4x4 card and leave three for future expansion

if it’s a boot risk i’ll just use a single carrier since i only need one, if that makes sense

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Yeah, I don’t see why it shouldn’t work but if it doesn’t, then just change as you reboot the system for maintenance / adding more drives. These cards are typically not hot-swappable in either case.

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understood, don’t intend on hot-swapping anything that isn’t sata and even then, not really the cage will be locked

yes, ive tested this with a gen 5 hyper m2 x16 card
slot 1 (x16), then 1+3 (x8x8), then 1-3 (4x4), then 1-4 for 1-4 m2 respectively

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legend mate, cheers