I start seeing occasional corruption around 1350 m...
# silicon-validation
a
I start seeing occasional corruption around 1350 mV Vcore and at 1250 it's much more pronounced
m
Are you using this same voltage for reading or just for retention? I wouldn't expect it to work at much less than the rated 1.8 for reads since read noise margins come into play pretty quickly. However, for retention, it could probably drop down to fairly low voltages as long as the voltage is ramped up for the read again.
This design doesn't have a decoupled read in the 6T cell which means that reads at low voltages can disrupt the contents of the memory.