Computer System Architecture Questions and Answers

Answer: B

The answer is a register.

Registers are a small set of very fast storage locations built into the processor itself. They hold the data, addresses and instructions the CPU is working on at that moment, for example the accumulator, the program counter and the instruction register. They are the fastest memory in the computer.

VLSI (very large scale integration) is a chip-making technology, not a storage place. A hard disk and a magnetic disk are secondary storage devices outside the processor, far larger and far slower than registers.

Answer: C

The one that is not secondary memory is Random Access Memory (RAM).

RAM is primary (main) memory: the processor works directly with it, it is fast, and it is volatile, losing its contents when power is switched off.

Solid state drives, hard disks and USB pen drives are secondary storage. They are non-volatile, keep data without power, and hold programs and files that are loaded into RAM when needed.

Answer: D

The memory that keeps its data without power is ROM.

Read-only memory is non-volatile: its contents, such as the firmware that starts the computer, are written in at manufacture or by special programming and stay when the power is switched off.

Static RAM, dynamic RAM and cache memory are all volatile. Dynamic RAM is the main memory, static RAM is faster and is used to build cache memory, and all of them lose their contents when power is cut.

Answer: D

The answer is a microprocessor.

A microprocessor is an integrated circuit that contains the whole central processing unit, the arithmetic logic unit, control unit and registers, on a single chip; modern ones have several cores on one chip.

The motherboard is the main circuit board on which the processor and other components are mounted, the control unit is only one part of the CPU, and a micro SSD is a storage device.

Answer: D

The answer is Cache.

Cache memory is a small, very fast memory built into or beside the CPU. It keeps copies of the data and instructions the processor uses most often, so they can be fetched far faster than from main memory.

RAM is the main working memory and is slower than cache. A hard drive is secondary storage, much slower again. ROM holds fixed start-up instructions such as firmware and is not used to speed up access to frequently used data.

Answer: D

Once written, a WORM disk behaves like a CD-ROM.

WORM stands for Write Once, Read Many. Data can be recorded on the disk a single time, after which it cannot be changed or erased and can only be read, which is exactly how a CD-ROM (Compact Disc Read-Only Memory) behaves.

RAM can be written and rewritten freely. An erasable optical (EO) disk can be erased and reused. A DVD is just a disc format that may be recordable or rewritable, so it does not describe the read-only behaviour as precisely as CD-ROM.

Answer: B

Flash EEPROM erases a block or the entire chip at once.

Traditional EEPROM is electrically erased one byte at a time. Flash memory is a type of EEPROM designed to erase whole blocks (or the full chip) in a single operation, which makes it much faster for large rewrites and is why it is called flash.

Erasing one byte at a time describes ordinary EEPROM, the very thing the question contrasts. Ultraviolet light is used to erase EPROM, not EEPROM or flash. Flash memory can be erased and rewritten many times, so 'cannot be erased' is wrong.

Answer: C

The answer is Assertion (A) is correct, but Reason (R) is incorrect.

The Assertion is true: the CPU exchanges information with memory over the address bus, data bus and control bus, which together form the system bus.

The Reason is false. The purpose of the system bus is to interconnect the CPU, memory and input/output devices so that they can communicate and work together, not to make them work independently without any interconnection. A false Reason rules out both options that call it correct.

Answer: B

The correct matching is 1-iii, 2-iv, 3-ii, 4-i.

• The program counter keeps track of the address of the next instruction to be executed (1-iii).
• The instruction register holds the instruction currently being decoded by the control unit (2-iv).
• The memory address register holds the address of the memory location to be read or written (3-ii).
• The accumulator holds operands and the intermediate results produced by the ALU (4-i).

A common mix-up is between the program counter and the MAR: both hold addresses, but the PC points to the next instruction while the MAR points to whatever location is being accessed now.

Answer: C

The main challenge is cache coherence.

When each processor keeps its own copy of shared data in its local cache, a write by one processor can leave stale copies in the others. Cache coherence is the problem of keeping all those copies consistent, solved by protocols such as MESI using bus snooping or a directory.

Cache replacement decides which block to evict when a cache is full. Cache partitioning divides a cache among cores or processes. Cache latency is the time an access takes. Each matters for performance, but none of them is about consistency between processors.