DMA Controller

DMA stands for direct memory access. The DMA controller is a control unit that can transfer data blocks between I/O devices and main memory with minimal intervention from the CPU. It also speeds up data transfer between I/O devices and memory.


A DMA Controller transfers 16-bit words to memory using cycle stealing.

The words are assembled from a device that transmits characters at a rate of 2400 characters/sec. The CPU fetches instructions at an average rate of 1 Million instructions/sec. By how much will the CPU be slowed down because of DMA transfer? (Each character is of 8 bits).

  1. 12%
  2. 12%
  3. 24%
  4. 24%