It doesn't surprise me that they have built in TDR type stuff as
the phy chip for 1000BaseT is sending and receiving data on
all 4 pairs of wire simultaneously, and so must subtract out
it's sent signal from it's received signal as well as remove
echos of it's own signal that come back from far-end reflections.
i.e. those phy chips end up being some pretty spiffy DSP engines
under the hood.  Just what you would need for doing TDR
type stuff.  They have the echo cancellation functions
so they need to be able to measure time for reflections already.

As to what is available in chipsets and their abilities - I don't
know of any that have TDR capabilities made available, but the last
time I looked at this was a couple of years ago when the 1000BaseT
standard had *just* been formalized.  I'm sure many more and
better chips have since come out.

Dan

M. Adam Davis wrote:

> My latest motherboard has built in 1000baseT (gigabit ethernet over
> twisted pair) and comes with a utility that tests cables.  It'll provide
> minimal TDR capabilities - in addition to the usual shorts/opens, it'll
> tell you where in the cable the short/open is, how long the cable is,
> various parameters about the cable, improperly connected pairs.  Some
> tests need a similar network card on the other end, but most run with
> just one end connected to this board.
>
> I'm hoping to find a PCI or PCMCIA card with this capability - it'll
> save me tons of time!  What I'd /really/ like is a handheld driving one
> of these cards.  It'd be neat to look at the chipset info and see if
> it's interfaceable with a low level controller...
>
> -Adam
>
> Howard Winter wrote:
>

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