Welcome Aboard – Chapter 1 COMP 2610 Dr. James Money COMP 2610 1.

Welcome Aboard – Chapter 1COMP 2610

Dr. James Money COMP 2610

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• Computer: electronic genius?▫NO! Electronic idiot!▫Does exactly what we tell it to, nothing more.

• Goal of the course:▫You will be able to write programs in C

and understand what’s going on underneath.

• Approach:▫Build understanding from the bottom up.▫Bits Gates Processor Instructions C

Programming

How We Will Get There

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Dr. James MoneyCOMP 2610

•Abstraction▫Allows us to be more productive

Can drive a car without knowing how the internal combustion engine works.

▫…until something goes wrong! Where’s the dipstick? What’s a spark plug? Do you understand how a car works?

▫Important to understand the components and how they work together.

Two Recurring Themes

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•Hardware vs. Software▫Most people refer to themselves as one who

specializes in hardware or software, but not both

▫You should take the opposite approach – it is good to know both and sometimes essential Hardware engineers added MMX instructions for video when this did not exist yet

Sorting can be dependent on the underlying hardware

▫You are seen as more versatile if you know both

Two Recurring Themes

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Computer Systems

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ca 1980It took 10 of these boards to

make a Central Processing Unit

ca 2000You can see why they called this CPU a microprocessor!

•When we mention computer systems, most people do not only think of the CPU.

•It usually includes the keyboard, mouse, monitor, video card, hard drive, and so on

•We focus on the CPU and how it does what we want it to do

Computer Systems

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1. All computers, given enough time and memory,are capable of computing exactly the same things. They are Universal Computing Devices

Two important concepts

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= =PDA

WorkstationSupercomputer

2.Problem Transformation▫The ultimate objective is to transform a problem expressed in natural language into electrons running around a circuit!

Two important concepts

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•Mathematical model of a device that can performany computation – Alan Turing (1937)▫ability to read/write symbols on an infinite

“tape”▫state transitions, based on current state

and symbol

•Every computation can be performed by some Turing machine. (Turing’s thesis)

Computers as Universal Computing Devices

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Turing Machines

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Tadda,b a+b

Turing machine that adds

Tmula,b ab

Turing machine that multiplies

For more info about Turing machines, seehttp://www.wikipedia.org/wiki/Turing_machine/

For more about Alan Turing, seehttp://www.turing.org.uk/turing/

• Also known as a Universal Computational Device: a theoretical device that accepts both input data and instructions as to how to operate on the data

Universal Turing Machine

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•U is programmable – just like a computer!• instructions are the input data•a computer can emulate a Universal

Turing Machine

•A computer is a universal computing device.

Computers as Universal Computing Devices

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•In theory, computer can compute anything that’s possible to compute given enough memory and time

•In practice, solving problems involves computing under constraints.▫time

weather forecast, next frame of animation, etc▫cost

cell phone, automotive engine controller, etc▫power

cell phone, handheld video game, etc

From Theory to Practice

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Transformations between layers

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Problems

Language

Microarchitecture

Circuits

Devices

Algorithms

Instruction Set Architecture

•We describe the problem initially in natural language

•This is inefficient▫There are ambiguities in the description

normally▫“Stir until soup is thick” has multiple

meanings to different people•We cannot have this ambiguity in

computer programs•We need precision

Statement of Problem

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•In order to make the problem precise, we turn it into an algorithm

•This process is called software design▫We choose algorithms and data structures

•An algorithm is a step by step procedure that is guaranteed to terminate such that each step is precisely stated and can be carried out by a computer.

•There are three terms for these properties.

Algorithm

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•Definiteness – each step is precisely stated

•Effective Computability – each step can be carried out by a computer. For example, you cannot ask a computer to find the largest prime number.

•Finiteness – the algorithm terminates.

Algorithm

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•There are many algorithms for each problems.

•There may be one with the fewest steps

•Others may allow concurrent computations

Algorithm

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•We now using programming to convert the algorithm to a program

•Programming languages are precise and invented to specify a sequence of instructions to the computer

•Over 1000 languages•There are two types of languages:

▫High level – C,C++,Pascal, Java▫Low Level – Assembly, one language for

each computer type

Program

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• Next, by compiling, we convert the programming language into the instruct set of the computer, called the ISA

• The ISA specifies what instructions the computer can perform, what values it needs, and it’s results

• We use the term operand to describe the values the instruction needs

• The ISA specifies acceptable representations for operands called data types

• The ISA also specifies where the operands are located called the addressing modes

Instruction Set Architecture(ISA)

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•Processor design results in the microarchitecture that runs the ISA

•The microarchitecture is the detailed particular implementations of the ISA

•There are many microarchitectures for each ISA▫Intel, AMD for x86▫Different models of Intel chips

Microarchitecture

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•We now implement the microarchitecture using simple logic circuits

•Here there is a cost tradeoff between cost and performance▫NOT gates are cheaper than regular ones

•Many choices just for a simple case of addition

•This is called the logic circuit design phase

Logic Circuit

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•Finally, process engineering and fabrication results in the devices used to build the logic circuits

•There might be CMOS, NMOS, and other types of circuits.

Devices

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Putting it together

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Solve a system of equations

Gaussian elimination

Jacobiiteration

Red-black SOR Multigrid

FORTRAN C C++ Java

Intel x86PowerPC Atmel AVR

Centrino Pentium 4 Xeon

Ripple-carry adder Carry-lookahead adder

CMOS Bipolar GaAs

Tradeoffs:costperformancepower(etc.)

• Bits and Bytes▫ How do we represent information using electrical signals?

• Digital Logic▫ How do we build circuits to process information?

• Processor and Instruction Set▫ How do we build a processor out of logic elements?▫ What operations (instructions) will we implement?

• Assembly Language Programming▫ How do we use processor instructions to implement algorithms?▫ How do we write modular, reusable code? (subroutines)

• I/O, Traps, and Interrupts▫ How does processor communicate with outside world?

• C Programming▫ How do we write programs in C?▫ How do we implement high-level programming constructs?

Course Outline

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Welcome Aboard – Chapter 1 COMP 2610 Dr. James Money COMP 2610 1.

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