Back in the old days we needed to make an Ethernet Crossover Cable to get this to work.

Modern ethernet supports Auto MDI-X, which manages that automagically for you.

> https://en.wikipedia.org/wiki/Ethernet_crossover_cable

I have no idea why we had red cables. There is absolutely no engineering reason why, when ethernet became a thing, that MDI-X wasn't sorted out automatically with some sort of signalling protocol. It was almost certainly a cost thing and that would probably been at the penny level (fuck customers - they don't cost me at the component stage).

To be fair, I don't know why USB had to wait until a few years back to stop acting quantum with its C incarnation. As you know a USB interface with two possible orientations will require at least three insertion attempts.

I grew up with RS232 and expected better. I had to wait quite a long time. USB C is quite good.

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gunalx 2 minutes ago | parent | next [-]

I hate how USBC is actually electrically directional. And that some shitty devices sont fully implement things properly so it still is only one way to insert it, but both work physically.

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ssl-3 5 hours ago | parent | prev [-]

It was, quite simply, a very different time. This stuff was designed in the nineteen eighties.

Old 10base-T ethernet used one pair of wires for transmit, and another pair of wires for receive (and the other 2 pairs? they did nothing at all!). This worked for the usual case of plugging computers into a hub.

It was Good Enough, and it fit the style of the time.

Could it have been done better? Sure! But that would have added complexity, and adding complexity means even more cost.

And all of this Ethernet hardware was already very expensive. A person who had enough money get into 10base-T hardware probably also had enough money to get a crossover cable in their hands.

The expense is why people like you and I grew up with using RS-232: That was the affordable way to get computers to talk together.

(Let me guess: You also had a run-in with 10base2 once that became cheap-enough, and you also spent way too long soldering together a cable to get PLIP going between a pair of computers)

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Anyway, auto MDI/MDI-X is pretty much a solved problem these days. At this point there are surely people reading these pages who have been doing stuff with computers and Ethernet for their entire lives and have never needed to know what a crossover cable is.

This, too, is Good Enough. :)

	▲	armada651 5 hours ago \| parent [-]
		I learned what a crossover cable was as a teenager because I was in an electronics store buying an ethernet cable and I picked the cool-looking black-and-red cable. Then the guy behind the counter told me that the cool-looking cable I picked is a special cable and instead handed me a boring grey cable. :(