Almost done, I promise. This is power domain 16 for anyone keeping count.
GTX_1V0, the digital core of the SERDES block. 999.901 mV average on a nominal 1.0V, absolutely nailed it! Ripple is 7.22 mV p-p / 0.85 mV RMS without any bandwidth limit. This is far enough inside the spec that I didn't even bother measuring within the specified 10 kHz - 80 MHz band.