Communication Protocols — question 9 of 10
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A board's Ethernet link light intermittently fails to come up, but only when the board is cold (just after power-on in a cool room); once it's been running a few minutes it links reliably every time. The PHY's status register reports 'no link partner detected' during the failures. Given the PHY/MAC split and the magnetics in the signal path, walk through where you'd look first, what you'd measure, and what you'd expect to see if your hypothesis is correct.