set-5

Answer: 4. All of these

Explanation:

• CPUs use various addressing techniques to access data and instructions in memory. The most common addressing techniques include:
  • Direct Addressing: The operand’s address is directly specified in the instruction.
  • Indirect Addressing: The instruction contains the address of a memory location that holds the actual address of the operand.
  • Immediate Addressing: The operand itself is included in the instruction, so no memory access is needed to fetch the operand.
• These techniques are fundamental to how CPUs process instructions and data efficiently.

Answer: 3. Optimizing compilers

Explanation:

• Optimizing compilers are designed to generate efficient machine code for pipelined systems. They rearrange instructions to minimize pipeline stalls and maximize throughput by ensuring that the CPU’s pipeline is utilized effectively. This is crucial for improving the performance of modern processors.

Answer: 2. Assembly line operation

Explanation:

• Pipelining in CPUs is often compared to an assembly line in manufacturing. Just as an assembly line divides a task into smaller stages performed simultaneously, pipelining divides instruction execution into stages (e.g., fetch, decode, execute, write-back) to improve throughput and efficiency.

Answer: 1. 1

Explanation:

• In pipelining, each stage (e.g., fetch, decode, execute) is designed to complete its task within one clock cycle. This ensures that instructions flow smoothly through the pipeline without delays, maximizing the CPU’s efficiency.

Answer: 3. Cache

Explanation:

• Cache memory is used to increase the speed of memory access in pipelined systems. It stores frequently accessed data and instructions closer to the CPU, reducing the time needed to fetch them from slower main memory. This helps prevent pipeline stalls and improves overall performance.

Answer: 1. Structural hazard

Explanation:

• A structural hazard occurs when multiple instructions in a pipeline compete for the same hardware resource (e.g., memory, ALU). This can cause delays or stalls in the pipeline, reducing its efficiency. Structural hazards are a common issue in pipelined architectures.

Answer: 1. Data hazard

Explanation:

• A data hazard occurs when an instruction depends on the result of a previous instruction that has not yet completed. This can happen in pipelined systems when instructions are executed out of order or when data is not yet available in the pipeline. Techniques like forwarding and stalling are used to resolve data hazards.

Answer: 4. Complex Instruction Set Computer

Explanation:

• CISC stands for Complex Instruction Set Computer. It is a type of CPU architecture that uses a large set of complex instructions, each capable of performing multiple low-level operations. CISC architectures aim to reduce the number of instructions per program, but they can be more complex to implement.

Answer: 2. RISC

Explanation:

• RISC stands for Reduced Instruction Set Computer. RISC architectures focus on simplifying the instruction set, allowing each instruction to execute in a single clock cycle. This reduces the time of execution and improves performance, especially in pipelined systems.

Answer: 3. Having a branch delay slot

Explanation:

• A branch delay slot is a feature in RISC architectures where the instruction immediately following a branch instruction is executed before the branch takes effect. This helps to minimize pipeline stalls caused by branches, improving performance in pipelined systems.

Answer: 3. Semantic gap

Explanation:

• The semantic gap refers to the difference between high-level programming languages and low-level machine instructions. Both CISC and RISC architectures aim to reduce this gap by providing instructions that align more closely with high-level operations, making programming easier and improving efficiency.

Answer: 1. RISC

Explanation:

• Pipelining is a key feature of RISC architectures. RISC processors are designed with simpler instructions that can be executed in a single clock cycle, making them ideal for pipelining. This allows multiple instructions to be processed simultaneously, improving throughput and performance.

Answer: 4. Transistors

Explanation:

• In CISC architectures, complex instructions are implemented using transistors on the CPU chip. These instructions are designed to perform multiple low-level operations in a single instruction, reducing the number of instructions needed for a program.

Answer: 1. Immediate addressing

Explanation:

• In immediate addressing, the operand is directly specified in the instruction itself. This means the value to be used is part of the instruction, and no additional memory access is required to fetch the operand.

Answer: 2. Register mode

Explanation:

• In register mode, the operand is placed in one of the CPU’s general-purpose registers (e.g., 8-bit or 16-bit registers). This mode is faster than memory-based addressing because the data is already in the CPU’s registers.

Answer: 1. 3

Explanation:

• An offset in addressing modes is typically determined by adding up to three address elements: a base address, an index, and a displacement. This combination allows for flexible and efficient memory addressing.

Answer: 1. TRUE

Explanation:

• Zero-address instructions use implied addressing mode, where the operands are implicitly defined by the instruction itself. For example, in stack-based architectures, the operands are always on the top of the stack, so no explicit address is needed.

Answer: 1. EA = 5 + R1

Explanation:

• In indexed addressing mode, the effective address (EA) is calculated by adding an offset (5 in this case) to the contents of a register (R1). The formula for the effective address is:
  $EA = 5 + R1$

Answer: 2. Relative

Explanation:

• Relative addressing mode uses the Program Counter (PC) as a base register. The effective address is calculated by adding an offset to the current value of the PC. This mode is commonly used for branching and jump instructions.

Answer: 1. Relative

Explanation:

• Relative addressing mode is ideal for changing the normal sequence of instruction execution because it allows branching to a new address relative to the current Program Counter (PC). This is commonly used in loops and conditional jumps.

Answer: 2. Negative numbers

Explanation:

• Sign magnitude is a method of representing negative numbers in binary. The most significant bit (MSB) represents the sign (0 for positive, 1 for negative), and the remaining bits represent the magnitude of the number.

Answer: 4. Negative Number

Explanation:

• In sign magnitude representation, a sign bit of 1 indicates a negative number, while a sign bit of 0 indicates a positive number.

Answer: 3. Higher voltage level

Explanation:

• In a positive logic system, a logic 1 is represented by a higher voltage level, while a logic 0 is represented by a lower voltage level. This is the standard convention in digital systems.

Answer: 1. m full adders

Explanation:

• An m-bit parallel adder consists of m full adders, one for each bit of the input numbers. Each full adder handles one bit of the addition, including the carry-in and carry-out for the next stage.

Answer: 2. Peripheral Devices

Explanation:

• Peripheral devices are external devices connected to a computer, such as keyboards, mice, printers, and monitors. They provide input to or receive output from the computer system.

Answer: 2. 3

Explanation:

• There are three main modes of I/O data transfer:
  1. Programmed I/O: The CPU directly controls the data transfer.
  2. Interrupt-driven I/O: The device interrupts the CPU when it is ready to transfer data.
  3. Direct Memory Access (DMA): The device transfers data directly to/from memory without CPU intervention.

Answer: 4. DMA

Explanation:

• Direct Memory Access (DMA) offers the highest speed for I/O transfers because it allows devices to transfer data directly to/from memory without involving the CPU. This reduces CPU overhead and speeds up data transfer.

Answer: 2. The I/O devices and the memory share the same address space

Explanation:

• In memory-mapped I/O, I/O devices and memory share the same address space. This means that I/O devices are accessed using the same instructions and addressing modes as memory, simplifying the programming model.

Answer: 1. IBM

Explanation:

• ISA (Instruction Set Architecture) is a standard developed by IBM to define the set of instructions that a CPU can execute. It serves as the interface between hardware and software.

Answer: 4. Parallel BUS

Explanation:

• The SCSI (Small Computer System Interface) BUS is a parallel bus used to connect devices like hard drives, scanners, and video devices to a processor. It provides high-speed data transfer and supports multiple devices on the same bus.

Answer: 2. 32 bit

Explanation:

• Many modern controllers use 32-bit registers to handle data and control signals efficiently. This allows them to process larger amounts of data and perform complex operations.

Answer: 3. 1000

Explanation:

• Auxiliary memory (e.g., hard drives, SSDs) has a much slower access time compared to main memory (RAM). Typically, auxiliary memory access time is about 1000 times slower than main memory.

Answer: 1. Hit/(Hit + Miss)

Explanation:

• The hit ratio is a measure of cache performance and is calculated as:
  $\text{Hit Ratio} = \frac{\text{Number of Hits}}{\text{Number of Hits} + \text{Number of Misses}}$
  A higher hit ratio indicates better cache performance.

Answer: 4. Both A and B

Explanation:

• Auxiliary memory includes storage devices like magnetic disks and tapes, which are used for long-term data storage. These devices are slower than main memory but have much larger storage capacities.

Answer: 4. Registers

Explanation:

• Registers provide the fastest data access because they are located directly within the CPU. They are used to store data that is currently being processed, enabling extremely fast access times.

Answer: 2. Main memory

Explanation:

• The memory hierarchy typically follows this order:
  Registers → L1 Cache → L2 Cache → Main Memory (RAM) → Secondary Storage. After the L2 cache, the next level is main memory.

Answer: 1. Complex Instruction Set Computer

Explanation:

• CISC (Complex Instruction Set Computer) processors often include multiclocks to handle complex instructions that may require multiple clock cycles to execute.

Answer: 2. Reduced Instruction Set Computer

Explanation:

• RISC (Reduced Instruction Set Computer) processors primarily use register-to-register data transfer. This simplifies the instruction set and improves performance by reducing memory access.

Answer: 2. RISC Focus on software

Explanation:

• RISC processors focus on software optimization by using a simpler instruction set. This allows compilers to generate more efficient code, improving overall performance.

Answer: 3. RISC

Explanation:

• RISC processors require more registers to support their register-to-register operations and reduce the need for memory access. This improves performance by keeping frequently used data in registers.

Answer: 1. Semantic gap

Explanation:

• Both CISC and RISC architectures aim to reduce the semantic gap between high-level programming languages and low-level machine instructions. This makes programming easier and improves efficiency.

Answer: 4. All of the above

Explanation:

• CISC processors have the following characteristics:
  • They use a microprogrammed control unit.
  • They support memory-to-memory data transfer.
  • Instructions are not strictly register-based, allowing for more complex operations.

Answer: 2. Cache Memory

Explanation:

• Cache memory is a small, high-speed memory located between the CPU and main memory. It stores frequently accessed data and instructions to reduce the time needed to access them from slower main memory.

Answer: 2. False

Explanation:

• Cache memory is typically implemented using SRAM (Static RAM) chips, not DRAM (Dynamic RAM). SRAM is faster and more expensive, making it suitable for cache memory.

Answer: 1. HIT

Explanation:

• When the CPU finds the required data in the cache memory, it is called a cache hit. This results in faster data access compared to a cache miss, where the data must be fetched from main memory.

Answer: 3. Least Recently Used

Explanation:

• LRU (Least Recently Used) is a cache replacement policy where the least recently accessed data is replaced when the cache is full. This helps to keep the most frequently used data in the cache.

Answer: 2. Inconsistent

Explanation:

• When the data in the cache does not match the data in the main memory, the cache is said to be inconsistent. This can occur due to write operations that update the cache but not the main memory.

Answer: 2. Write within

Explanation:

• The common write policies to maintain cache coherence are:
  • Write through: Data is written to both the cache and main memory simultaneously.
  • Write back: Data is written only to the cache and later written to main memory when the cache line is replaced.
  • Buffered write: Data is temporarily stored in a buffer before being written to memory.
  • Write within is not a valid write policy.

Answer: 1. Snoopy writes

Explanation:

• Snoopy writes is an efficient method for cache updating in multiprocessor systems. It involves monitoring the bus for memory updates and invalidating or updating cache lines accordingly to maintain coherence.

Answer: 1. Associative

Explanation:

• In fully associative mapping, any block of main memory can be mapped to any line in the cache. This provides maximum flexibility but requires more complex hardware to search the cache.