Question 9971 – Shortest-Path
November 11, 2023C-Programming
November 11, 2023Question 9794 – Secondary-Storage
Consider a disk with following specifications: 20 surface, 1000 tracks/surface, 16 sectors/track, data density 1 KB/sector, rotation speed 3000 rpm. The operating system initiates the transfer between the disk and the memory sector-wise. Once the head has been placed on the right track, the disk reads a sector in a single scan. It reads bits from the sector while the head is passing over the sector. The read bits are formed into bytes in a serial-in-parallel-out buffer and each byte is then transferred to memory. The disk writing is exactly a complementary
process.
For parts (c) and (d) below, assume memory read-write time = 0.1 microsecond/byte, interrupt driven transfer has an interrupt overhead = 0.4 microseconds, the DMA initialization and termination overhead is negligible compared to the total sector transfer time. DMA requests are always granted.
- (a) What is the total capacity of the disk?
(b) What is the data transfer rate?
(c) What is the percentage of time the CPU is required for this disk I/O for bytewise interrupts driven transfer?
(d) What is the maximum percentage of time the CPU is held up for this disk I/O for cycle-stealing DMA transfer?
Correct Answer: A