Why is the width of the data bus so important to the processing speed of a computer?

The width and clock rate of the data bus determine the number of bytes per second that it can carry, which is one of the main factors determining the processing power of a computer. Most current processor designs use a 32-bit bus, meaning that 32 bits of data can be transferred at once. A data bus can transfer a data to and from the main memory of a computer, or into or out of the CPU that acts as the device's "engine".