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I had stated the electron’s don’t care whether the wires are twisted.
What I added to that, and maybe didn’t emphasize enough, was that they care about the transmission and interference parameters of the channel – not its physical construction. These parameters can be achieved by PCB traces, shielded pairs, coax, or other means. The two applications fit within the same set of transmission (and interference) parameters – then the physical construction is outside our scope (a problem left for the implementer).
Having done this for a number of decades, I firmly believe it is possible and even likely that the same PHY developed for the short-reach channel will serve the need for the backplane application. There is a long history of using ethernet PHYs both for cabled and backplane channels. BASE-X PHYs have been used on coax & board traces, 1000BASE-T has been used on backplanes, and even run on open-wire, DSL transceivers (Ethernet in the First Mile) have been similarly used both on traces, open wire, twisted pair, and even coax.
Additionally, we are not saying that the same chip is used both in backplane and, for example, automotive applications – only that it is the same, interoperable PHY description. There are other requirements on the chips, for example, the thermal environment, which may make them different chips. However, if you plug two PHYs of the same specification into a common link segment, they should work interoperably (at least at the PHY level).
George Zimmerman, Ph.D.
President & Principal
CME Consulting, Inc.
Experts in Advanced PHYsical Communications