dma2 madeeasy TB

Question

An i/o device transfers data at the rate of 10 MBPS over a 100 MBPS bus. The data is transferred in 4 KB blocks.if the processor operates at 500 megahertz and it takes a total of 5000 cycles to handle is DMA request find the fraction of CPU time handling the transfer with and without DMA.

Answer 1

time to transfer 4KB bock = 4x10^3 / 10^7 => 400 microsec

time to handle request = 5000 / 500 x 10^6 => 10 microsec

fraction of time c.p.u is blocked = 10 / 410