Suppose that a system uses DMA for data transfer from disk controller to main memory. Further assume that it takes $t_{1}\: nsec$ on average to acquire the bus and $t_{2}\:nsec$ to transfer one word over the bus $(t_{1} >> t_{2}).$ After the CPU has programmed the DMA controller, how long will it take to transfer 1000 words from the disk controller to main memory, if
- word-at-a-time mode is used,
- burst mode is used?
Assume that commanding the disk controller requires acquiring the bus to send one word and acknowledging a transfer also requires acquiring the bus to send one word.