Don’t do this with your boards – this is just a test 🙂
Do you know all the tough rules from PCB design guides – length matching, impedance, etc.? What do you think, how far you can go and brake them?
I was curious. We have not finished our baseboard yet and I really wanted to test our Ethernet PHY. So I had an opportunity to wire up a magnetics to the 1Gb Ethernet PHY on the module and test it. And I did. See this picture:
Do you know what? It worked 😀 The Ethernet is running at 1Gb speed (even I have not used an exact impedance nor did a precise length matching). I have not measured the real throughput, but it works.
BTW: 10 years ago, I wired up DDR266 memories (swapped DQS & DQM signals between banks) and it worked too – at least on my table in the lab 😉
Please, this doesn’t mean, that you should not follow design guides. You definitely should. Why? It may look like everything is working ok, but that may not be true. Always try to design your board the best as you can.