Consider a computer system with DMA support. The DMA module is transferring…
2021
Consider a computer system with DMA support. The DMA module is transferring one 8-bit character in one CPU cycle from a device to memory through cycle stealing at regular intervals. Consider a 2 MHz processor. If 0.5% processor cycles are used for DMA, the data transfer rate of the device is __________ bits per second.
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Correct answer: 80000
Answer: 80,000 bits per second
Working:
Processor clock = 2 MHz = 2,000,000 cycles per second.
DMA uses 0.5% of cycles: 0.005 × 2,000,000 = 10,000 DMA cycles per second.
Each DMA cycle transfers one 8-bit character, so data rate = 10,000 × 8 = 80,000 bits per second.
Therefore, the device data transfer rate is 80,000 bits per second.
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