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In article ,
(Sam Nelson) writes:
I used to run about 3km of thick and thin Ethernet in ceiling voids, and
there was never a TDR on the market cheap enough for `them' to let me get one.
I wrote an ethernet driver for the first ethernet chipset, the AMD LANCE
7990. That has a built-in TDR, and when the cable broke, our systems
(GEC 4000 minicomputers) output on the console the TDR values, which is
the number of 10MHz clock cycles which pass between transmitting the
preamble and seeing its reflection from a cable break. Customers found
this incredibly useful, and many picked a quiet time and went round
their networks breaking the ethernet every 10 metres or so to record
the TDR values the GEC 4000's generated, so when it broke for real, they
could instantly home in on the 10m region of suspect cable. To this day,
I remain amazed that no one else ever seems to have put this feature into
an ethernet driver (although with switched twisted pair networks, it's
now become redundant). OK, it's not as fine grained as a separate TDR
instrument, but it was damn useful on networks of 10base5 and 10base2
that were around for many years.
--
Andrew Gabriel
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