FreeLists / si-list / [SI-LIST] Re: purpose of 8b/10b encoding

["Jeffrey J. Cook" <jjcook@xxxxxxxx>]

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

Generally as I understand, it is to be able to recover the clock by
ensuring some number of transitions per period (8 per 10?). Clocks change
period frequently when working at high speeds, due to temperature, etc... not
to meantion the fact that otherwise the sending clock would inevitably be
out of phase, plus period, of your receiver's clock.

# 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)?

Unfortunately I'm not familiar with Infiniband, but assume that they
send the clock inside the data to ensure the clock experiences the exact
same delay as the data.  Plus it saves a wire!

--
Jeffrey J. Cook
Electrical Engineering Master's Degree Candidate
University of Illinois at Urbana-Champaign
jjcook@xxxxxxxx

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