A computer system is provided. In one embodiment, the computer system includes a memory, a peripheral device, a central processing unit (CPU), and a peripheral device controller. The CPU stores information about the data transmission in a descriptor in the memory when data transmission between the CPU and the peripheral device is required. The peripheral device controller reads the descriptor from the memory at an access frequency, records whether the descriptor read from the memory requests for data transmission as a recording result, and adjusts the access frequency according to the recording result.