DMA module

Question

A DMA module is transferring characters to memory using cycle stealing, from a device transmitting at 12800 bits per second.The processor is fetching instructions at the rate of 2MIPS. By how much % the processor be slowed down due to DMA activity?

Comments

How much data is to be transferred?

Answer 1

1) assuming 1 character = 8 bit

Number of character 1600

In cycle s stealing mode 1 byte per transfer

1600 bytes in 1 second

1 byte in 625 micro second.

2 MIPS so time for single instructions fetch 0.5 micro second

So involment of processor will be 0.5

0.5/625 =  0.08%