Intro to Architecture

Fall 2003, Final Exam

Please answer all questions carefully and thoughtfully.
Use as much paper as you wish, but make sure that you label your answers and that you put your name on the top of each page.
Unreadable or incomprehensible answers will receive no credit.

(7 pts) A keyless entry system has a special embedded CPU to support its operations. The system receives a command from a key fob, and performs the action specified by the command. Design a machine language for this CPU. Discuss the reasons behind your design. The commands are:
- Unlock Trunk
- Unlock Doors
- Open Trunk
- Open Door N (N= Driver Front, Passenger Front, Driver Rear, Passenger Rear, ALL)
- Start Engine
(5 pts) The x86 processor is capable of addressing two bytes of memory without respect to alignment, but this costs an extra memory cycle. What does this mean? Give a plausible explanation for the extra cost.
(3 pts) Most sparc assemblers provide for pseudo-ops or operations such as
```
Clear R3
```
```
Copy R2, R2
```
which are not implemented in the ISA, but are useful for programmers. Why does the ISA for the sparc lack these instructions?
(5 pts) Use the conditional sum algorithm to add 10100101₂ and 10100110₂
(5 pts) What is a floating point number? Describe how to represent a floating point number in a computer. Give the format for an IEEE 754 floating point number, you may ignore the denormals.
(5 pts) We discussed three types of hazards in a pipelined machine. Name and describe one. Describe how this hazard can be overcome.
(5 pts) Describe what is required in an assembly language/machine implementation to support a language that has recursive subroutines.
(10 pts) The instruction
```
 Load R2, R3[R4]
```
will load the memory contents at R4+R3 into R2. Discuss how this example can be used to support the following programming language constructs
1. Pointers
2. Arrays of integers
3. Structures
4. Arrays of Structures
(5 pts) Describe the differences between CISC and RISC architectures.