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UNC-Chapel Hill COMP 004 - LECTURE NOTES

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Computer architecture part 2 lecture topic What we ll cover for this What affects overall processing speed More about physical components KEEP UP with textbook readings The Boot Process If RAM is empty when I turn on the computer how does the CPU know how to start up and how to load the Operating System What else happens at boot up Remember RAM s cousin ROM Excellent text coverage Read pages 44 47 COMP 4 Power Tools for the Mind What s in the 1 INPUT PROC OUTPU T 0025 CPU CU ALU Pointer operand op code Address reg Instr reg operand op code operands Address reg of a single machine language instruction 35 Register In a basic machine 1 instruction 350 cycle Accumulator 1 execution cycle 10 35 10 350 Register Adder Storage register Machine cycle processing Memory Program 1 Inputs Op code Operands Op code Operands Op code Operands Data file 1 Program 1 Program 2 Program 3 Aux Storage COMP 4 Power Tools for the Mind Outputs Program 4 Data file 1 Data file 2 What s in the 2 What affects overall processing speed The clock is one measure of processor speed CPUs use a digital clock pulse to synchronize the activities of the different hardware units An ALU performs one step of an execution operation each time a clock pulse occurs The number of cycles required to process complex instructions varies among instructions and CPUs Hence an complex instruction with 20 steps will have a duration of 20 clock cycles Number of cycles Hz per second Clock speed EG 800 MHz clock 800 million clock ticks second 800 million steps occur per second machine cycles What s in the COMP 4 Power Tools for the Mind 3 So an 800 MHz processor is twice as fast as a 400 MHz processor right Wrong If an 800 MHz processor requires 15 cycles to perform a complex instruction it will probably do worse than a 400 MHz processor that requires only 5 cycles for that same complex instruction Within same processor class clock speed might be a fair performance indicator Within the same processor class AND if all else is equal then an 800 MHz processor is almost twice as fast as a 400 MHz processor COMP 4 Power Tools for the Mind What s in the 45 Word size Longer is better more manipulated at once Number of bits the CPU can store manipulate as a unit during a single basic machine cycle Early PCs 8 bit processor then 16 bit 1st IBM PC Today s PCs 32 bit latest 64 bit designs for servers and high end PCs Bus IF all else is equal a 32 bit processor will be twice as fast as a 16 bit processor width More is better more carried at once Bus pathways wires along which bits pulses travel w in CPU and the rest of computer system Bus connects ALU and CU CPU with memory input devices with memory etc Data bus Address bus Note Address BUS WIDTH determines amount of addressable memory the CPU can access COMP 4 Power Tools for the Mind What s in the 5 COMP 4 Power Tools for the Mind What s in the 6 Main memory DRAM dynamic More is better Today s apps are memory hogs Amount of main memory available to the processor and its access speed affects OVERALL performance Update of old adage You Can never be too rich too thin or have TOO MUCH RAM Cache More is better Processor idle while it waits for memory access to finish Cache logically lies between CPU and main memory Computer attempts to keep a copy in cache of that portion of main memory that is of current interest SRAM static Those transfers normally made between RAM CPU registers are made between cache and CPU registers instead Caching Expensive but improves overall processing speed significantly COMP 4 Power Tools for the Mind What s in the 7 Logical organization between main memory and CPU CPU registers Cache Inputs lies between Primary Memory Outputs Auxiliary Storage Hard disks floppy disks CD ROMs tape COMP 4 Power Tools for the Mind What s in the 89 Physical organization can be on chip and or off chip On chip cache Off chip cache COMP 4 Power Tools for the Mind What s in the 9 Digression Memory storage hierarchy Fastest to slowest access smallest to largest capacity Registers Memory Cache Level1 Level2 Primary Memory Auxiliary secondary mem storage a hierarchy exists within this category as well Disk faster than tape hard disk faster than Floppy disk etc COMP 4 Power Tools for the Mind What s in the 1011 Other architectural designs that affect speed We won t discuss here JUST FOR CULTURE Instruction set complexity CISC and RISC Pipelining Miniaturization Number of processors Serial one CPU Parallel More than one co processors or multiple processing units COMP 4 Power Tools for the Mind What s in the 11 12 Discussing speed Many functions are measured in terms of how quickly they can be performed during some portion of a second or how many can be done in 1 second Millisecond thousandth several milliseconds for disk access Microsecond millionth memory speed processor speed for many PCs Nanosecond billionth processor speed in higher end PCs Picosecond trillionth processor speed in supercomputers Quotable COMP 4 Power Tools for the Mind What s in the 12 More about physical components Transistor elementary building block Drain Semi Conductor Gate Source Solid state switch can switch states in less than 20 nanoseconds Less than 1 micron wide 0 11 0 25 microns Gate Drain CHANNEL Source SILICON SUBSTRATE COMP 4 Power Tools for the Mind What s in the 13 The chip transistors capacitors resistors paths and other components form the IC VLSI level of integration and miniaturization Packing it in less distance for signals to travel faster Electric pulses travel through a wire 1 foot nanosecond Some chip types and transistor densities Memory chips RAM ROM etc EG a 64Mbit IC has 70 80 million transistors Microprocessor chips CPU for general purpose PCs The number of transistors on a chip has increased more than 18 000 times since 1971 For example 1971 only 2 300 transistors on the 4004 chip 2001 42 million on the Pentium 4 Coming 214 million COMP 4 Power Tools for the Mind What s in the 14 15 The Chip Individual transistors Newer generation microprocessors high end 18 micron wide transistors 42 million transistors chip Pins connectors that allow communications with other chips Plug into circuit board socket Package Circuit board Bus commun Channels http www intel com intel intelis museum COMP 4 Power Tools for the Mind What s in the 15 16 Digital Electronics and Input and Output devices GOOD textbook coverage Chapter 2 pages 62 thru 64 Chap 2 pages 88 thru 96 So we WON T COVER HERE System board Expansion slot


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