Computer System Architecture Questions and Answers

Answer: A

Correct answer: MIPS = Instruction count/(Execution time)10^6

MIPS means millions of instructions per second, so the instruction count is divided by the execution time in seconds and then by 10⁶ to convert to millions:

\[ \text{MIPS}=\frac{\text{Instruction count}}{\text{Execution time}\times 10^{6}} \]

Dividing by 10³ would give thousands of instructions per second, and omitting the divisor gives plain instructions per second.

Answer: B

Correct answer: Control Unit

The control unit fetches each instruction, decodes it, and issues the enable and timing signals that make the ALU, registers and memory carry it out. The ALU performs the operations rather than directing them, and the CPU is the whole of which the control unit is one part.

Answer: B

Correct answer: Peripheral devices

Peripherals - printers, keyboards, disk drives, tape units - are electromechanical and electromagnetic devices of some complexity, in contrast with the purely electronic circuits of the CPU and memory. Printing devices and input devices are both classes of peripheral, so naming either of them alone is too narrow.

Answer: D

Correct answer: both a and b

In symmetric multiprocessing every processor is a peer: all of them run the operating system and all of them reach main memory over the same system bus. So both the bus and the memory are shared. The processors themselves are the things doing the sharing, not a resource that is shared.

Answer: B

Correct answer: B is 9.1 times as fast as A for programs

The machine with the shorter execution time is the faster one, and the ratio of the times gives the factor:

\[ \frac{1001\ \text{ns}}{110\ \text{ns}}=9.1 \]

B takes 110 ns against A's 1001 ns, so it is B that is 9.1 times as fast, not A.

Answer: D

Correct answer: 2

Execution time is the number of CPU clock cycles divided by the clock rate:

\[ \text{Execution time}=\frac{\text{CPU clock cycles}}{\text{Clock rate}}=\frac{4}{2}=2 \]

Answer: C

Correct answer: Memory Space

The set of addresses that physically exist in main memory is the memory space; the set of addresses a program may generate is the address space. Keeping the two apart is the basis of virtual memory, where the address space is larger than the memory space.

Answer: C

Correct answer: Interrupt driven I/O

With interrupt-driven I/O the processor issues the transfer and then continues with other work; the device raises an interrupt when it is ready, so the CPU never sits polling. Programmed I/O ties the processor up in a wait loop, and DMA removes the processor from the transfer altogether rather than letting it run a program concurrently with it.

Answer: D

Correct answer: Pulse generator

A digital system is timed by a train of clock pulses produced by a pulse generator; the clock is the signal, not the source. A decoder or a counter distributes or divides that signal but does not create it.

Answer: A

Correct answer: In Accumulator

The accumulator is the register that holds one operand of an arithmetic or logic operation and receives the result. Cache and ROM are memory rather than working registers, and the instruction register holds the instruction being executed, not its result.