1. Computer Operations
Part 2

2. Many, Many Simple Operations
Computers have small instr. set
Decoder may only recognize 100 instr
About 20 kinds of operations
All other operations must be reduced to these

3. Cycling the Fetch/Execute Cycle
ADD is average complexity instr.
CPUs execute many such instr / sec
MIPS
FLOPS, GFLOPS, TFLOPS

4. The Computer Clock
CPUs are instruction execution engines, synchronized by clock
Clock speed measured in ticks / sec (Hz)
Clock cycles are short
2 GHz => cycle time of 0.5 ns

5. Standard Prefixes

6. One Cycle per Clock Tick
Perspective
Light travels about 1 ft / ns
CPUs try to start an instr. on each clock tick

7. One Cycle per Clock Tick
CPUs use pipelining
Overlap instr. execution
Laundry analogy

8. Schematic Fetch/Execute Cycle

9. A Computer’s View of Software

10. Computer’s View of Software
Executable program
Binary object file
Sequence of 4-byte groups (words)
Can be millions of words long

11. Computer’s View of Software
CPU executes program by
copying binary instructions into RAM
interpreting them using Fetch/Execute Cycle

12. Assembly language
CPU only “speaks” machine language (executes binary object files)
Near impossible to write binary code
What to do?
Need higher-level language and translation
Assembly => object code
E.g.: ADD 15, 21, 19 => …001

13. Assembly language Assembly language uses letters and #s
Computer scans assembly code
Looks up words in table to convert to binary
Converts #s to binary
Assembles binary pieces into object file

14. Programming Languages
Most programs written in High-level programming language
Translated (compiled) to assembly
Assembled to binary

15. JavaScript Fragment

16. Operating Systems Operating system (OS) Most popular OS’s?
Manages resources
Most popular OS’s?
Microsoft Windows
Apple's Mac OS X
Unix / Linux

17. Operating Systems Sits atop h/w Responsible for Apps OS Hardware
Booting
Process, memory, file, and device management

18. Programming Programmers utilize s/w stack Software stack
Layers of software of increasing complexity
Higher-level abstractions toward top

19. Integrated Circuits (ICs)
“Chip”
Electrical components integrated into silicon
Smaller = faster
Speed of light

20. Photolithography Photolithography: process of making IC
Si wafer covered with light-sensitive photoresist and patterned mask
Exposed to uv light which causes open areas to harden
(unexposed areas are washed away leaving pattern)
Hot gases etch original layer
When remaining photoresist is removed, the pattern from mask remains

23. Making a CPU Intel: From Sand to Silicon – the Making of a Chip

24. How Semiconductor Technology Works
Silicon is semiconductor
Making chip entails controlling conductivity

25. How Semiconductor Technology Works
Searching for red AND giant

26. On-Again, Off-Again Two switches can compute logical AND
Other combinations of switches in ALU perform
AND OR
NOT
etc.

27. Transistors
Transistor
Controllable switch
Key component in IC

29. Big Picture: Running App
Start with information-processing task
Task is performed by a program
Program consists of instr.
Instr. were written in high-level language, but have been compiled and assembled into binary code
CPU uses Fetch/Execute cycle to run instr.

30. Summary
Computer
CPU
ALU CU
Memory
Storage
I/O
Fetch/Execute Cycle

31. Summary Machine instructions Programming languages Software stack
Integrated circuits

32. Quiz 
What part of the CPU is responsible for arithmetic and logical operations?
Memory is a sequence of cells, each of which can hold 1 ___________.
The last stage of the Fetch/Execute cycle is ____________.