Basics of RISC and CISC Architectures
What is a characteristic of RISC architecture?
A) Small and simple instruction set
B) Complex and variable-length instructions
C) Support for multiple addressing modes
D) Emphasis on microcode
Answer: A) Small and simple instruction set
Which architecture typically has more complex instructions, RISC or CISC?
A) CISC
B) RISC
C) Both are equally complex
D) Neither
Answer: A) CISC
In RISC architecture, what is typically the size of instructions?
A) Fixed size
B) Variable size
C) Dynamic size
D) None of the above
Answer: A) Fixed size
Which architecture often uses multiple clock cycles to execute a single instruction?
A) CISC
B) RISC
C) Both RISC and CISC
D) Neither
Answer: A) CISC
RISC architectures often focus on which aspect to improve performance?
A) Pipelining and instruction-level parallelism
B) Complex instructions
C) Microcode interpretation
D) Extensive addressing modes
Answer: A) Pipelining and instruction-level parallelism
Instruction Set and Complexity
Which of the following is true about CISC instructions?
A) They can perform multiple operations in a single instruction.
B) They are typically simple and uniform.
C) They are always fixed in length.
D) They focus on single-cycle execution.
Answer: A) They can perform multiple operations in a single instruction.
What is a typical feature of RISC instructions?
A) Simple operations and a uniform instruction format
B) Complex addressing modes
C) Support for microcode
D) Multi-cycle execution for each instruction
Answer: A) Simple operations and a uniform instruction format
Which architecture uses a larger number of general-purpose registers to minimize memory access?
A) RISC
B) CISC
C) Both
D) Neither
Answer: A) RISC
CISC processors generally require more complex hardware to handle what aspect of instruction execution?
A) Instruction decoding and execution
B) Register allocation
C) Pipelining
D) Instruction fetch
Answer: A) Instruction decoding and execution
RISC architectures are designed to perform operations in how many clock cycles on average?
A) One clock cycle
B) Two to three clock cycles
C) Multiple clock cycles
D) Variable number of clock cycles
Answer: A) One clock cycle
Code Generation Principles
Which of the following is a key consideration in code generation for RISC architectures?
A) Instruction scheduling for pipelining
B) Complex addressing modes
C) Variable-length instructions
D) Microcode optimization
Answer: A) Instruction scheduling for pipelining
In CISC architectures, code generation often involves what process?
A) Complex instruction decoding
B) Simple register allocation
C) Uniform instruction format
D) Minimal use of addressing modes
Answer: A) Complex instruction decoding
Which architecture often benefits from code generation techniques that focus on instruction reduction?
A) CISC
B) RISC
C) Both
D) Neither
Answer: B) RISC
In RISC architectures, how is instruction scheduling typically managed?
A) By optimizing instruction pipelines
B) By using variable-length instructions
C) By decoding instructions into multiple micro-operations
D) By managing complex addressing modes
Answer: A) By optimizing instruction pipelines
What is a common goal of code generation for CISC architectures?
A) Efficient use of complex instructions
B) Minimizing the number of instructions executed
C) Reducing the number of registers
D) Simplifying instruction formats
Answer: A) Efficient use of complex instructions
Register Allocation
Which architecture typically emphasizes register allocation to minimize memory accesses?
A) RISC
B) CISC
C) Both
D) Neither
Answer: A) RISC
In CISC architectures, how is register allocation often handled?
A) By leveraging the complex instructions that use memory directly
B) By minimizing the number of registers available
C) By using a fixed set of registers
D) By focusing on a small number of registers
Answer: A) By leveraging the complex instructions that use memory directly
RISC architectures often utilize what kind of register model?
A) A large number of general-purpose registers
B) A small number of special-purpose registers
C) A fixed register model with few general-purpose registers
D) A register model with no registers
Answer: A) A large number of general-purpose registers
In CISC code generation, what is a typical approach to handling operations involving memory?
A) Using complex instructions that access memory directly
B) Performing all operations in registers
C) Avoiding memory operations entirely
D) Using only immediate values
Answer: A) Using complex instructions that access memory directly
Which approach to register allocation is more common in RISC architectures?
A) Register-to-register operations
B) Memory-to-register operations
C) Immediate value operations
D) Direct memory access
Answer: A) Register-to-register operations
Addressing Modes
What is a common feature of addressing modes in CISC architectures?
A) Support for a wide range of addressing modes
B) Simple and uniform addressing modes
C) Fixed addressing mode
D) Limited addressing modes
Answer: A) Support for a wide range of addressing modes
Which addressing mode is typically emphasized in RISC architectures?
A) Register addressing
B) Memory indirect addressing
C) Immediate addressing
D) Complex addressing modes
Answer: A) Register addressing
In which architecture is the use of complex addressing modes more common?
A) CISC
B) RISC
C) Both
D) Neither
Answer: A) CISC
RISC architectures often rely on which type of addressing mode for most operations?
A) Register addressing
B) Indexed addressing
C) Base-register addressing
D) Immediate addressing
Answer: A) Register addressing
Which addressing mode is used by CISC processors to directly access operands from memory?
A) Direct addressing
B) Register addressing
C) Indirect addressing
D) Indexed addressing
Answer: A) Direct addressing
Instruction Scheduling
Which technique is commonly used in RISC architectures to enhance performance through instruction scheduling?
A) Out-of-order execution
B) Microcode interpretation
C) Complex instruction decoding
D) Multiple clock cycles for each instruction
Answer: A) Out-of-order execution
CISC processors often use which technique to handle complex instructions?
A) Microcode
B) Instruction pipelining
C) Register renaming
D) Out-of-order execution
Answer: A) Microcode
What is the primary goal of instruction scheduling in RISC architectures?
A) To optimize the execution of instructions by the pipeline
B) To decode complex instructions efficiently
C) To handle variable-length instructions
D) To manage multiple clock cycles
Answer: A) To optimize the execution of instructions by the pipeline
In CISC architectures, instruction scheduling may be impacted by what factor?
A) The complexity of instructions and their variable length
B) Fixed instruction length
C) Simple instruction formats
D) Uniform instruction execution time
Answer: A) The complexity of instructions and their variable length
What role does instruction pipelining play in RISC architectures?
A) It allows overlapping execution of multiple instructions to improve performance
B) It simplifies instruction decoding
C) It handles complex instructions with multiple micro-operations
D) It reduces the number of general-purpose registers
Answer: A) It allows overlapping execution of multiple instructions to improve performance
Procedure Call Handling
In RISC architectures, how is procedure call handling typically managed?
A) Using a fixed-size stack frame and simple calling conventions
B) Using complex stack frames and variable conventions
C) By minimizing the use of procedures
D) By using extensive microcode
Answer: A) Using a fixed-size stack frame and simple calling conventions
Which architecture often requires more complex handling for procedure calls and returns?
A) CISC
B) RISC
C) Both
D) Neither
Answer: A) CISC
What is the common approach for handling procedure calls in CISC architectures?
A) Using a variety of calling conventions and complex stack management
B) Using fixed-size stack frames and simple conventions
C) Minimizing the use of procedures
D) Avoiding procedure calls
Answer: A) Using a variety of calling conventions and complex stack management
What is a typical feature of procedure call handling in RISC architectures?
A) Simplicity in stack management and calling conventions
B) Complexity in instruction handling
C) Use of microcode for calls
D) Variable-size stack frames
Answer: A) Simplicity in stack management and calling conventions
CISC architectures often use what technique for efficient procedure calls?
A) Using complex instructions that combine multiple operations
B) Fixed-size stack frames
C) Out-of-order execution
D) Register renaming
Answer: A) Using complex instructions that combine multiple operations
Advanced Topics
What is “loop unrolling” in the context of code generation for RISC architectures?
A) Expanding loops to reduce the overhead of loop control and increase performance
B) Repeating loops multiple times
C) Reducing the number of instructions in a loop
D) Simplifying loop instructions
Answer: A) Expanding loops to reduce the overhead of loop control and increase performance
In CISC architectures, what is a key challenge related to instruction encoding?
A) Managing the variable length and complexity of instructions
B) Ensuring fixed instruction length
C) Simplifying instruction formats
D) Minimizing the number of instructions
Answer: A) Managing the variable length and complexity of instructions
What is “instruction-level parallelism” in RISC architectures?
A) The ability to execute multiple instructions simultaneously
B) The use of complex instructions
C) The handling of variable-length instructions
D) The optimization of single instructions
Answer: A) The ability to execute multiple instructions simultaneously
In CISC architectures, what is a typical approach to optimize instruction execution?
A) Using microcode to handle complex instructions
B) Using fixed instruction formats
C) Simplifying instruction execution
D) Reducing the number of registers
Answer: A) Using microcode to handle complex instructions
Which approach is commonly used in RISC architectures to reduce instruction count and improve performance?
A) Code optimization techniques like loop unrolling and instruction scheduling
B) Complex addressing modes
C) Variable-length instructions
D) Extensive use of microcode
Answer: A) Code optimization techniques like loop unrolling and instruction scheduling
Code Generation Challenges
What is a major challenge in code generation for CISC processors?
A) Managing the complexity and variety of instructions
B) Simplifying instruction execution
C) Fixed instruction length
D) Uniform instruction format
Answer: A) Managing the complexity and variety of instructions
In RISC code generation, what is typically minimized to improve performance?
A) Memory access and instruction complexity
B) Register usage
C) Fixed instruction length
D) Instruction set size
Answer: A) Memory access and instruction complexity
What is the role of “instruction scheduling” in optimizing code for RISC processors?
A) To improve pipeline utilization and reduce stalls
B) To manage complex instruction formats
C) To handle variable-length instructions
D) To simplify microcode execution
Answer: A) To improve pipeline utilization and reduce stalls
How does “code motion” optimization benefit CISC architectures?
A) By moving code out of frequently executed paths to reduce overhead
B) By simplifying instruction encoding
C) By increasing instruction length
D) By minimizing memory accesses
Answer: A) By moving code out of frequently executed paths to reduce overhead
What is “register renaming” used for in RISC architectures?
A) To eliminate false data dependencies and increase parallelism
B) To handle complex instructions
C) To manage variable-length instructions
D) To simplify instruction formats
Answer: A) To eliminate false data dependencies and increase parallelism
Miscellaneous Topics
Which of the following techniques is often used in RISC architectures to optimize code execution?
A) Branch prediction and speculative execution
B) Microcode expansion
C) Complex instruction formats
D) Extensive use of memory operations
Answer: A) Branch prediction and speculative execution
What is a key advantage of using a fixed instruction length in RISC architectures?
A) Simplified instruction decoding and pipelining
B) Increased instruction complexity
C) Variable-length instruction formats
D) Complex addressing modes
Answer: A) Simplified instruction decoding and pipelining
Which architecture often employs “micro-operations” to break down complex instructions?
A) CISC
B) RISC
C) Both
D) Neither
Answer: A) CISC
What is the typical impact of “instruction fetch” on CISC architectures?
A) It can be affected by the complexity and variable length of instructions
B) It is simplified due to fixed instruction length
C) It does not impact performance
D) It reduces the need for pipelining
Answer: A) It can be affected by the complexity and variable length of instructions
How does “out-of-order execution” benefit RISC processors?
A) By allowing instructions to be executed as soon as their operands are ready, increasing overall performance
B) By simplifying instruction formats
C) By using complex instruction formats
D) By minimizing the number of registers
Answer: A) By allowing instructions to be executed as soon as their operands are ready, increasing overall performance