Like any other electronic device, the console needs power. The power supply is quite
complex and has to generate several voltages to run all the chips. It is composed of
dual 7805 linear 5V regulators
One of the 5V regulators supplies power to the PIC micro, and the other supplies power to the analog circuitry (video and audio).
The 3.3V regulators drive the audio DAC.
And a switch-mode power supply was used to generate the 1.5V core voltage and 3.3V I/O voltage for the FPGA. The 3.3V is also used by the DRAM chip and some other parts on the board.