Computer System Architecture Questions and Answers

Answer: C

Correct answer: Execution time

Execution time is the only measure that cannot be gamed: it counts the whole job on the actual machine. A higher clock rate may be spent on more cycles per instruction, and an instruction set says nothing about how fast the instructions run, so neither is a reliable measure of performance on its own.

Answer: A

Correct answer: SPEC benchmark

SPEC - the Standard Performance Evaluation Corporation - publishes the suites of CPU-intensive integer and floating-point programs used to compare machines. The other three names are not benchmark suites.

Answer: A

Correct answer: hot standby mode

In asymmetric clustering one machine runs the application while the other does nothing but monitor it, ready to take over the instant it fails. A machine kept powered and ready in this way is in hot standby; plain standby would not imply that it is already running and watching.

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.