Industry Expert Blogs

Pop quiz! Which section of the PCI Express Base Specification covers bifurcation? Here, I’ll even wait while you look….

Did you give up yet? Good. First of all, you won’t find the word “bifurcation” in the spec at all! The term is commonly understood to mean splitting a set of PCI Express lanes into multiple links – and it’s most common on Root Complexes. So for example, our friendly neighborhood Root Complex (RC) vendor builds an RC with 16 lanes – but he knows that in some uses the RC will connect to a single x16 link, while in others his customers only want x4 links. Rather than waste the 12 now unused lanes, wouldn’t it be nice to instead be able to configure those 16 total lanes as 4 links each of x4 width?

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