Re: XAUI and 64b/66b
> The 64b/66b proposal as written ignores the XGXS block between
> XAUI and the PCS. It is my contention that, though this would
> work, it is unnecessary and even burdensome to those implementors
> that choose to not use XAUI. 64b/66b would work equally as well
> without the XAUI specific control codes as they add nothing to
> the efficiencies of 64b/66b (that I can tell). The XGMII specific
> control codes are completely adequate for 64b/66b. In my opinion,
> a serial PCS should be specified as if XAUI didn't exist.
> I'll even go so far as to state that, in my opinion, even a
> parallel/CWDM PCS should be specified as if XAUI didn't exist.
> If this PCS turns out to be identical to the XGXS block then some
> implementors may choose to avoid the encode/decode/encode as
> specified in the standard, but I believe that is how it should
> be specified.
This was the reason the XGXS block was split into two (although I did
not believe it was necessary) --- to make it crystal clear that the XAUI
is optional and all the PCSs will be spec'ed to the XGMII.