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Direct memory access

(also DMA)

Direct memory access definition

Direct memory access is a process that enables specific hardware subsystems, like peripheral devices, to access a computer's primary memory (RAM) directly without requiring the involvement of the CPU. This functionality boosts the efficiency and speed of data transfer, thereby freeing the CPU resources for other activities. DMA is widely employed in network adapters.

See also: CPU utilization

Direct memory access examples

  • Sound cards: When playing audio files, DMA allows the sound card to read data directly from memory, minimizing CPU usage and ensuring smooth playback.
  • Graphics cards: In graphic-intensive applications or games, DMA enables the graphics card to access textures and other graphical data from memory, improving rendering performance.
  • Network adapters: DMA facilitates efficient data transfer between the computer's memory and the network adapter, reducing latency in network communications.

Comparing direct memory access to other data transfer methods

  • Programmed I/O: In this method, the CPU is responsible for transferring data between peripherals and memory, resulting in higher CPU usage and slower data transfer rates compared to DMA.
  • Interrupt-driven I/O: This method uses interrupts to notify the CPU when data is ready to be transferred but still requires the CPU to handle the transfer. While it offers better performance than programmed I/O, it lacks the efficiency of DMA.

Pros and cons of direct memory access


  • Enhanced data transfer speed and efficiency.
  • Reduced CPU usage, freeing resources for other tasks.
  • Improved performance in devices requiring high-speed data access.


  • Increased complexity of hardware and software design.
  • Potential for conflicts between devices sharing the same DMA channel.

Tips for using direct memory access

Ensure that DMA-compatible devices are properly configured in the BIOS settings or operating system to take full advantage of the performance benefits offered by DMA.