This again is a question for Austin:
The recommended operating conditions for spartan-3 are VCCINT < 1.26V. What will happen if I power it with 1.28V?
Antything more serious than a live expectancy reduced from 20 years to15 years?
You know, there a only a few small 1.2V regulators on the market but there a plenty of 1.25V versions around. But those have a tolerance of a few percent...