What Is an Accelerated Processing Unit?

Alex Newth

An accelerated processing unit (APU) is a blend of a central processing unit (CPU) chip and a graphics processing unit (GPU) chip, which adds many benefits over using a CPU exclusively. While the GPU initially was made solely for loading graphics, it can be used in an accelerated processing unit to take on some general CPU tasks. The two chips are working together and they are placed on the same section, so the tasks of both chips can be done with less power. One problem with an APU is that few sub-processors are used, and a CPU with many sub-processors may be able to work faster than an APU.

Many computers are built with sole CPUs because they work faster and often outperform an APU.
Many computers are built with sole CPUs because they work faster and often outperform an APU.

The CPU and GPU traditionally were two separate chips and, while the CPU was used for most of a computer’s processing, the GPU optimized memory to best load graphics. With an accelerated processing unit, both of these chips are right on top of each other, so both chips work simultaneously. Combining the chips like this has proven to increase processing power, and it also increases the computer’s speed.

The GPU was made to optimize image loading but, when combined with a CPU, it also can perform other processing. With an accelerated processing unit, the CPU is still used for generic processing and the GPU is used for graphics processing, but there is a relationship between the CPU and GPU that increases processing speeds. When the CPU has smaller tasks, it can push them off to the GPU so the CPU can use its power for large computations while the GPU uses its limited generic processing for smaller computations.

Less power is needed to run an accelerated processing unit for several reasons. The CPU can offset smaller tasks, so this energy is saved; the two chips are in the same area, too, so there is no need to waste energy moving data over larger expanses. While the power savings are not large, it means laptops can run longer without being plugged in and desktops will not get quite as hot when running.

While an accelerated processing unit improves on the sole CPU processing used in most computers, a strong CPU by itself may be able to work faster than an APU. This is because the APU does not use, nor does it have much room for, many sub-processors. These help increase a CPU’s power, and because a sole CPU has room for more sub-processors, a CPU may outperform an APU in general processing.

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