From Newsgroup: comp.arch

I was looking up info on PCI-E transfer rates, and discovered the kind
of encoding they use nowadays to keep the signal frequency bandwidth
reasonable <https://en.wikipedia.org/wiki/64b/66b_encoding>.

I had previously read up on EFM (as used on CDs and DVDs), and
according to the above, earlier versions of PCI-E used 8b/10b, which
is a similar sort of idea, pushed a little bit further. But with
64b/66b and other similar encodings, determinism has gone completely
out the window now, and they rely on purely statistical techniques to
ensure that bit patterns with troublesome frequency components are not impossible, but just vanishingly unlikely to occur.
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