“I think there is a world market for about five computers.”Thomas J.Watson (1945)Computer Abstractions and TechnologyIntroduction• Performance from a historical perspective – during our lifetime• The oft quoted comparison with transport industry• Computer as an intellectual tool, a consumer item, and an appliance• Speed vs performance– Add memory; new model being hierarchical memory– Increase clock speed; new model being add [specialized] processors; parallel processing• Why study computer architecture?Classical Hardware• Communication with a computer– Hitchhikers’ Guide to the Galaxy– The ultimate answer: 42.– The question: What do you get when you multiply nine by 6?– Do you see a problem here?• Binary arithmetic– Based on binary numbers, implemented by a simple switch with two states: off (or 0) and on (or 1)– Binary digit or bit– Instructions are simply numbers the computer understands to perform a job∗ I could tell you that when I say 0, the class is dismissed :-)– Binary numbers are used for both instructions and data• Assembler– The primitive way to communicate with the computers in a human-like language– Instead of issuing a command like3E 01 02to add two numbers (01 and 02 are locations where these numbers are kept), a programmer could saysomething likeADD A, B– Is it improvement? A simple program (assembler) will create the binary equivalent from the human-likelanguage• Next step in the evolution ladder – compilerIntroduction 2– Translate a more English-like (or mathematical notation) language to binary– Allows for increase in productivity of a programmer– Resulted in languages like cobol that were truly verbose– A C statement such asc = a + b;would be written in cobol asADD A TO B GIVING C.– High-level languages made the programs somewhat machine independent• Subroutine libraries– Collection of functions to perform tasks needed by many programs– Used for math functions, such as square root and trigonometry– Also used for I/O• Operating system– Ultimate control program to control system resources∗ System software∗ Application softwareOrganization of a simple computer• cpu, memory, storage devices, I/O devices, peripheral devices• Mouse– A basic pointing device– Can be used to determine the position in two dimensions– Optical vs mechanical mice• Monitor– Raster cathode ray tube (crt), achieved through an electron gun– Refresh rate of between 30 to 90 Hz– Image composed of pixels (picture elements)– Display matrix or bitmap– Simplest display – 1 bit per pixel (bpp)– Gray scale display – 256 gray scale values per pixel, or 8 bpp– Color display – 8 bpp for each of the three primary colors (red, green, blue), giving 24 bpp per pixel∗ A total of 224colors, or 16 million different colors– Liquid crystal display (lcd)∗ Thin, low power display∗ Rod shaped molecules in a liquid that bend the light entering the display, possibly from behind thedisplay– Bit map stored in a frame buffer or raster refresh buffer• MotherboardIntroduction 3– A plastic board containing packages of chips, including processors, cache, memory, and connectors for I/Odevices such as networks and disks– Processor or Central Processing Unit (cpu) is the guy who does all the work; this is the brain– Memory keeps all program code and data while the program undergoes execution∗ Read-only memory (rom)∗ Random Access Memory (ram)– Hierarchical memories∗ dram – Dynamic random access memory∗ Cache – Small fast memory to act as a buffer for dram– Abstraction∗ Hiding lower level details in abstract concepts∗ Sending output to print device– Instruction set architecture (isa)∗ Abstraction of hardware∗ Interface between hardware and low-level software∗ Consider the relationship between machine code and assembly language, and go one step down∗ Abstraction allows for multiple implementations implementations of the same isa– Backward compatibility of new isa∗ Macintosh changed from 68000-based machines to PowerPC∗ Intel tried to keep the basic isa in successive generations of the 80x86 family, starting from original8086 to latest Pentium Pro– Magnetic disks, or secondary memory∗ dram is volatile∗ Magnetic hard disk retains the information when power is turned off∗ Organized as a collection of platters, rotating on a spindle at constant speed· The disks on my Sun Blade 100 rotate at 7200 rpm∗ Movable arm with read/write head∗ About 5-10 ms for data access compared to 5-20 ns for dram– Communications∗ Information exchange between computers at high speed∗ Sharing of resources such as disks and I/O devices∗ Accessing machines remotely∗ Ethernet or lan· High speed network, typically 1 mb per sec· Limited to one mile∗ wan· Backbone of the internet· Based on optical fibers· May not be as fast as EthernetIntegrated Circuits• Transistor – a simple on/off switch• An ic combines zillions of transistors on a single chipIntroduction 4• vlsi – Very Large Scale ic, with gazillions of transistors on a single chip• Silicon– Basic building block of ics– Known as semiconductor because it does not conduct electricity very well• Chip building requires adding materials to silicon so that it can– conduct electricity very well– insulate electricity very well– conduct or insulate like a switch• vlsi manufacturing– Start with an ingot of silicon crystal, 6-12” in diameter and 12-24” long– Create wafers no more than 0.1” thick– Process by creating patterns of chemicals to create conductor, insulator, and switch regions– Process may result into imperfections, and so, a number of dies are created on each wafer– Imperfect dies are discarded, with good dies bonded to wires or I/O pins in a package, called