[SI-LIST] purpose of 8b/10b encoding

  • From: "Zabinski, Patrick J." <zabinski.patrick@xxxxxxxx>
  • To: si-list@xxxxxxxxxxxxx
  • Date: Mon, 10 Sep 2001 19:10:57 -0500

What's the purpose of 8b/10b encoding?

I've heard reasons ranging from "to provide DC-Free data
streams" to "to reduce the effective spectral content of
the link".   This is all fine-and-dandy, but the efficiency-
hit 8b/10b (80%) has on a link is a hefty price to pay.
I have a difficult time believing the benefits outweigh
the cost.

For links such as InfiniBand (and others), does anyone know
why 8b/10b encoding was used?  What are folks trying to accomplish
when they add this requirement to the spec(s)?

I'm sure there's something I'm missing here, and I'd appreciate
it if someone could clue me in.

Thanks,
Pat Zabinski

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