I would assume that the primary difference between 10base-t vs 100base-t is the speed of the clocks interpreting the electrical signal. In other words, if you ensure that a "bit" is transmitted in 1 micro-second, you could fit 10Mb of data down the wire in a second. If you ensured that a bit is transmitted in 1 nano-second, you could fit 100Mb in a second.

If that's the only difference, then every "100base-t" cable should be able to support transmitting data at 10Mbps as well.

Is this true? Or is my initial assumption wrong and there's more that's physically different between those two protocols?

1 Answer 1


(a bit simplified) 10baseT and 100baseTX (their most common variants, that is) both need 2 twisted pairs of cabling, but they use different line codings ("Manchester Code" vs "MLT-3"). While 10BASE-T can cope with Cat3, 100BASE-TX needs Cat5 rating.

Your assumption is correct: (some corner cases of 100basesomething left aside) any cable that supports 100BASE-TX will also support 10BASE-T.

More details at: https://en.wikipedia.org/wiki/Ethernet_over_twisted_pair

  • Actually, Category-3 cabling is only rated for 10 Mbps. Category-4 (no longer registered) was rated for 16 Mbps, and Category-5 (no longer registered) was rated for 100 Mbps. Category-5e replaced Category-5 in 1999, and it is rated up to 1000 Mbps.
    – Ron Maupin
    Commented Oct 1, 2018 at 22:06
  • 2
    edited while you were commenting... Commented Oct 1, 2018 at 22:07
  • 1
    Actually, 100BASE-TX uses 4b/5b PCS encoding before MLT-3, both together replacing 10BASE-T's Manchester. MLT-3 alone isn't self-clocking.
    – Zac67
    Commented Oct 2, 2018 at 11:39

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