Computer Basics

How exactly does a computer work?

Integrated Circuits

Integrated circuits (ICs) are the power source of the information revolution

When computers were made of discrete parts, wires of every transistor (3), capacitor (2), resistor (2), etc. had to be hand-connected

Labor intensive, expensive, error prone, unreliable, cumbersome, … even with robots!

Integrated circuits solved that by 2 ideas

Integration -- circuits built as a unit from like parts

Photolithography -- printing process to make chips

Photolithography

Consider process for depositing wires

Remove Resist

R4400 NEC/MIPS Processor

Semiconductors

Silicon, a semiconductor -- sometimes it conducts and sometimes it doesn’t

It’s possible to control when semiconductors do and don’t conduct

Ex.: Use control to test Mars AND rover

Field Effect

Charged objects are familiar -- use a nylon comb on a dry day

A charged field can control whether a semiconductor conducts or not

The charge of the control wire (gate) is key

Neutral gate, channel doesn’t conduct

Charged gate, channel conducts

MIPS R10000 Processor

MOS Transistors

The field effect idea is implemented in metal-oxide-semiconductor transistors

Operation

The two cases: the gate is neutral or the gate is charged

Computers ...

Deterministically execute instructions to process information

“Deterministically” means that when a computer chooses the next instruction to perform it is required by its construction to execute a specific instruction based only on the program and input it is given

Fetch/Execute Cycle

Computer = instruction execution engine

The fetch/execute cycle is the process that executes instructions

Anatomy of a Computer

Memory ...

Programs and their data must be in the memory while they are running

Control

The Fetch/Execute cycle is hardwired into the computer’s control, i.e. it is the actual “engine”

Indirect Data Reference

Instructions tell where the data is, not what the data is … contents change

ALU

The Arithmetic/Logic Unit does the actual computation

Input/Output

Input units bring data to memory from outside world; output units send data to outside world from memory

Most peripheral devices are “dumb” meaning that the processor assists in their operation

Disks are memory devices because they can output information and input it back again

The PC’s PC

The program counter (PC) tells where the next instruction comes from

Instructions are a word long, so add 4 to the PC to find the next instruction

Clocks Run The Engine

The rate a computer “spins around” the Fetch/Execute cycle is controlled by it’s clock

Current clocks run 2-3 GHz

In principle, the computer should do one instruction per cycle, but often it fails to

Modern processors try to do more than one instruction per cycle, and often succeed

Summary

Semiconductors make Info Revolution

Semiconductors properties ...

Fields controls when semiconductor conducts

On/off of conductors allows us to compute

Fetch/execute cycle runs instructions

5 steps to interpret machine instructions

Programs must be in the memory

Data is moved in and out of memory


Integrated circuits (ICs) are the power source of the information revolution
	When computers were made of discrete parts, wires of every transistor (3), capacitor (2), resistor (2), etc. had to be hand-connected
	Labor intensive, expensive, error prone, unreliable, cumbersome, … even with robots!
	Integrated circuits solved that by 2 ideas
		Integration -- circuits built as a unit from like parts
		Photolithography -- printing process to make chips


	Silicon, a semiconductor -- sometimes it conducts and sometimes it doesn’t
			It’s possible to control when semiconductors do and don’t conduct


			Ex.: Use control to test Mars AND rover


	Charged objects are familiar -- use a nylon comb on a dry day
			A charged field can control whether a semiconductor conducts or not


			The charge of the control wire (gate) is key
			Neutral gate, channel doesn’t conduct
			Charged gate, channel conducts


	The field effect idea is implemented in metal-oxide-semiconductor transistors


	Deterministically execute instructions to process information
			“Deterministically” means that when a computer chooses the next instruction to perform it is required by its construction to execute a specific instruction based only on the program and input it is given


	Computer = instruction execution engine
			The fetch/execute cycle is the process that executes instructions


	Programs and their data must be in the memory while they are running


	The Fetch/Execute cycle is hardwired into the computer’s control, i.e. it is the actual “engine”


	Instructions tell where the data is, not what the data is … contents change


	Input units bring data to memory from outside world; output units send data to outside world from memory
			Most peripheral devices are “dumb” meaning that the processor assists in their operation
			Disks are memory devices because they can output information and input it back again


	The program counter (PC) tells where the next instruction comes from
			Instructions are a word long, so add 4 to the PC to find the next instruction


	The rate a computer “spins around” the Fetch/Execute cycle is controlled by it’s clock
			Current clocks run 2-3 GHz
			In principle, the computer should do one instruction per cycle, but often it fails to
			Modern processors try to do more than one instruction per cycle, and often succeed


Semiconductors make Info Revolution
	Semiconductors properties ...
		Fields controls when semiconductor conducts
		On/off of conductors allows us to compute
Fetch/execute cycle runs instructions
	5 steps to interpret machine instructions
	Programs must be in the memory
	Data is moved in and out of memory