This application note (PDF!) from TI provides on-card regulation for logic circuits:
Because of the relatively high current requirements of digital systems, there are a number of problems associated with using one centrally-located regulator. Heavy power busses must be used to distribute the regulated voltage. With low voltages and currents of many amperes, voltage drops in connectors and conductors can cause an appreciable percentage change in the voltage delivered to the load. This is aggravated further with TTL logic, as it draws transient currents many times the steady-state current when it switches.
These problems have created a considerable interest in on-card regulation, that is, to provide local regulation for the subsystems of the computer. Rough preregulation can be used, and the power distributed without excessive concern for line drops
The local regulators then smooth out the voltage variations due to line drops and absorb transients.