Editing Macintosh II (section)

=== Power Supply and Thermal Design ===

The Macintosh II employed a sophisticated power supply design rated at 230 watts, providing multiple voltage rails: +5V, +12V, -5V, and -12V. The power supply included Power Factor Correction (PFC) circuitry, unusual for personal computers of the era, improving efficiency and reducing harmonic distortion.

Thermal management was accomplished through a multi-zone cooling system with temperature-controlled fans. The main system fan operated at variable speeds based on internal temperature sensors, while the power supply included its own dedicated cooling. This design allowed the system to operate quietly under normal conditions while providing adequate cooling under heavy loads.