Which processor size will consume the least amount of power, all other things being equal?

The ideal choice that represents the processor size consuming the least amount of power is the 28 nm size. This is because smaller process sizes, such as 28 nm, generally allow for transistors to be packed more densely, which can lead to reduced power consumption and improved performance.

As transistor sizes decrease, the voltage needed for operation also tends to decrease, which directly influences the power drawn by the processor. Additionally, smaller transistors have reduced gate capacitance, which further contributes to lower power consumption when switching states. Therefore, the 28 nm process provides a good balance of efficiency and power consumption compared to larger sizes.

While 45 nm and 65 nm processes are larger than 28 nm and typically consume more power due to higher operating voltages and increased capacitance, the 32 nm process is also larger than 28 nm but smaller than 45 nm and 65 nm, making it a reasonable alternative. However, it does not surpass the efficiency of the 28 nm process.

In summary, the 28 nm processor size stands out for its ability to minimize power consumption while maximizing performance capabilities, resulting from modern semiconductor manufacturing techniques that enable efficient design and operation.