Computer Architecture - RISC ISA Concepts

Questions and Answers

What is one main advantage of RISC design regarding the design cycle compared to CISC processors?

CISC processors have shorter design cycles.

RISC processors require more microcode.

RISC processors can be implemented more quickly. (correct)

RISC architectures are more complex to design.

How does the simplicity of RISC processors affect chip area utilization?

It consumes additional chip area.

It limits the number of registers available.

It allows for more performance-critical resources. (correct)

It increases the complexity of the layout.

What does RISC provide that makes it easier for programmers in terms of instruction handling?

A more complex instruction set.

A uniform instruction set. (correct)

More intricate program debugging.

Increased instruction count variability.

Which of the following is a consequence of the shorter design cycles of RISC processors?

They allow the use of the latest technologies sooner. Signup and view all the answers

What is one of the key distinctions between RISC and CISC architectures regarding condition codes?

RISC processors do not use condition codes. Signup and view all the answers

Why is code optimization measurement easier in RISC architectures?

Due to a higher correlation between instruction count and cycle count. Signup and view all the answers

What role does advanced semiconductor technology play in RISC processors?

It introduces tighter limits on transistor counts. Signup and view all the answers

How does using a stack for procedure arguments differ from using registers in RISC architecture?

The stack is less effective than registers. Signup and view all the answers

What is the primary benefit of pipelining in a CPU?

It enables simultaneous execution of multiple instructions. Signup and view all the answers

What is another term for interface registers in a pipelined processor?

Buffers Signup and view all the answers

In a 4-stage pipelined processor, which execution method results in the total time being reduced?

Overlapped execution Signup and view all the answers

How is the operation of each stage in a pipelined processor controlled?

Through a centralized common clock. Signup and view all the answers

What does the execution sequence of instructions in a pipelined processor resemble?

A space-time diagram. Signup and view all the answers

Which statement accurately describes non-overlapped execution in a pipelined processor?

No instruction executes until the prior one finishes. Signup and view all the answers

What is a key feature of a RISC processor's instruction pipeline?

It typically has a 5-stage pipeline. Signup and view all the answers

Which of the following best describes the relationship between the stages in a pipelined processor?

Each stage outputs to the next stage's input. Signup and view all the answers

What is a primary reason RISC processors can be implemented with fewer transistors than CISC processors?

RISC processors are simpler in design. Signup and view all the answers

Which programming approach does RISC architecture primarily support?

High-level language programming Signup and view all the answers

What is a primary measure of compiler efficiency in RISC architecture?

The compactness of generated code and execution time. Signup and view all the answers

Why do compilers produce code that often reflects a narrow subset of the processor instruction set architecture (ISA)?

Simple, well-defined operations lead to fewer side effects. Signup and view all the answers

Which of the following describes the relationship between RISC architecture and optimizing compilers?

RISC complements optimizing compilers by enabling effective instruction sequencing. Signup and view all the answers

What is a common characteristic of compilers that are part of the MIPS RISCompiler language suite?

They provide tight integration across various languages. Signup and view all the answers

What is a significant challenge compilers face when working with complex instructions?

Complex instructions often do not meet the requirements of high-level languages. Signup and view all the answers

What aspect of instruction streams was found to consume the most execution time during analysis?

Performing load and store operations Signup and view all the answers

What is the primary advantage of pipelining in instruction execution?

It allows multiple instructions to be processed simultaneously. Signup and view all the answers

In the R3000 pipeline, what function does the instruction decode stage perform?

Decodes the fetched instruction. Signup and view all the answers

How does the R4000 improve upon the R3000 in terms of clock cycle?

It reduces the clock cycle time to 30 ns. Signup and view all the answers

Which operational stage overlaps with instruction decode in a branch instruction?

Register fetch. Signup and view all the answers

What is the role of the ALU operation in the instruction pipeline?

To generate addresses for data operands. Signup and view all the answers

What change in the R4000 allows for higher density on the chip?

Incorporation of on-chip instruction and data caches. Signup and view all the answers

What is the significance of the 60 ns timing mentioned for external instruction and data access?

It indicates the time it takes for cache access operations. Signup and view all the answers

Why is the tight coupling between instructions beneficial in a pipelined architecture?

It allows for immediate use of results from previous instructions. Signup and view all the answers

Which languages are supported by the MIPS language suite's industry-standard front ends?

C, FORTRAN, Pascal Signup and view all the answers

What is the primary benefit of the common back-end in the MIPS language suite?

It exports optimizing and code-generating improvements throughout the language suite. Signup and view all the answers

What ensures that user programs conforming to the MIPS ISA execute on any hardware implementation?

The R4000 processor's application software compatibility. Signup and view all the answers

How many general-purpose registers does the R4000 processor contain when operating fully in 64-bit mode?

32 general-purpose 64-bit registers Signup and view all the answers

What is the expected execution rate of the R4000 processor due to its superpipeline design?

One instruction per cycle Signup and view all the answers

What role does the Memory Management Unit (MMU) play in the R4000 processor?

It provides rapid virtual-to-physical address translation. Signup and view all the answers

What is the size of the primary instruction and data caches in the R4000 processor?

8 Kbytes each Signup and view all the answers

What can be the maximum size of each primary cache architecturally increased in the R4000 processor?

32 Kbytes Signup and view all the answers

Study Notes

RISC Design and Benefits

RISC (Reduced Instruction Set Computer) architectures simplify design, enhancing performance through reduced complexity.
Shorter design cycles enable quick implementation compared to CISC (Complex Instruction Set Computer) processors, allowing adaptation to new technologies before obsolescence.
RISC's simplicity utilizes chip area effectively, facilitating larger register files, TLBs (Translation Lookaside Buffers), and fast arithmetic units, which boost performance.
User benefits from a uniform instruction set that eases usage, correlating instruction count with cycle count for better code optimization.
Compilers are optimized for RISC, focusing on high-level language programming, contrasting older CISC emphasis on assembly language, leading to more efficient machine code generation.

MIPS RISCompiler Language Suite

The MIPS RISCompiler language suite integrates multiple compilers with shared elements, supporting languages like C, FORTRAN, and Pascal.
It features a common intermediate language and unified object formats, enabling mixed-language programming and efficient debugging.
This integration promotes high-quality compilers and immediate updates across languages, enhancing maintenance and supporting user investment.

R4000 Processor Features

The R4000 processor maintains compatibility with previous MIPS models (R2000, R3000, R6000), ensuring user programs run on all MIPS hardware.
It has 32 general-purpose 64-bit registers, with instructions uniformly sized at 32 bits.
An efficient superpipeline design achieves nearly one instruction executed per clock cycle, adeptly handling pipeline stalls and exceptions.
Includes an on-chip memory management unit (MMU) for swift virtual-to-physical address translation.

Cache Control

R4000 features primary instruction and data caches, sized up to 8 Kbytes, extendable to 32 Kbytes; off-chip secondary caches can range from 128 Kbytes to 4 Mbytes.
The R4400 processor variant allows each primary cache to increase to 16 Kbytes.

Instruction Pipelining

Pipelining enhances CPU performance by executing multiple instructions simultaneously instead of sequentially.
Basic pipeline design includes several stages, with interface registers between stages to hold intermediate outputs.
RISC processors utilize a 5-stage pipeline: instruction fetch, operand fetch, ALU operation, data reference, and register write-back.
Each clock cycle may be split, increasing efficiency by enabling overlaps in instruction processing.

Comparative Execution

Non-overlapped execution takes longer as each instruction waits for its turn, while overlapped execution reduces total time significantly, achieving faster instruction processing through pipelining.

Advanced R4000 Technology

R4000 technology halves clock cycle time to 30 ns, improving register file access, and enabling on-chip caches.
Enhanced features maintain performance improvement while maximizing chip density and efficiency in instruction and data handling.

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Description

This quiz covers key concepts related to the Instruction Set Architecture (ISA) of RISC (Reduced Instruction Set Computer) systems. It focuses on the interaction between the memory and registers, and the distinctions in implementation programs. Test your understanding of condition codes and how they affect machine-level programming.