Week 5

Question 1

What is ARM7TDMI

Answer 1

• 32 bit microcontroller
• Von Neumann architecture (later processors use modified harvard architecture)
• 32 bit data bus so memory physically divided into 4 chips (memory banking)
• 32 bit address bus (physical memory)
• 32 bit instructions
• 37 registers

Question 2

Compare 8086 x86 architecture and ARM7 architecture

Answer 2

8086:
- Instruction length varies from 1 to 6 bytes
- Misaligned data is allowed
- ALU works with both memory and registers
- Typical CISC architecture

ARM7:
- All instructions have the same length
- Only accept aligned data
- ALU operations only work with registers
- Typical RISC architecture

Question 3

What is CISC and RISC

Answer 3

CISC - complex instruction set computer
RISC - reduced instruction set computer

• instruction set is the complete set of all the instructions in machine code that can be recognised and executed by the CPU
• There is a fixed number of instructions that the CPU understands

Question 4

CISC vs RISC

Answer 4

CISC:
- Various size instruction
- Multiple fetch cycles
- Operation on memory and registers
- Multiple execution cycle
- Many addressing modes
- Large and complex instruction set
- Decoding: complex
- Poor pipelining
- Flexible but slow
- More power consumption
- Example: Intel x86

RISC:
- Fixed size instruction
- One fetch cycle
- Operation mostly on registers
- Less addressing modes
- Reduced and simple instruction set
- One execution cycle
- Decoding: simple
- Superior pipelining
- Rigid but fast
- Less power consumption
- Examples: ARM

Question 5

ARM7 Pipeline

Answer 5

3-stage pipeline (fetch decode execute)