COMP 4—Power Tools for the Mind 1 What’s in the box? Computer architecture, part 2 What we’ll cover for this lecture topic: –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

COMP 4—Power Tools for the Mind 2 What’s in the box? Machine cycle: processing of a single machine-language instruction In a basic machine: 1 instruction cycle 1 execution cycle CPU Memory CU Program 1: Op-code Operands Op-code Operands … Data file 1 Pointer Storage register Address reg 0025 Instr. reg. ALU op-code operands op-code operand Aux. Storage Program 1 Program 2 Program 3 Program 4 Data file 1 Data file 2 Adder Register Accumulator Inputs Outputs INPUT/PROC/OUTPUT 35*10=

COMP 4—Power Tools for the Mind 3 What’s in the box? 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)

COMP 4—Power Tools for the Mind 4 What’s in the box? –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. 5 –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

COMP 4—Power Tools for the Mind 5 What’s in the box? 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) IF all else is equal, a 32-bit processor will be twice as fast as a 16-bit processor. Bus 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 6 What’s in the box?

COMP 4—Power Tools for the Mind 7 What’s in the box? Main memory 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. –Those transfers normally made between RAM & CPU registers are made between cache and CPU registers instead. –“Caching” –Expensive---but improves overall processing speed significantly! DRAM dynamic SRAM static

COMP 4—Power Tools for the Mind 8 What’s in the box? Logical organization: (between main memory and CPU) 9 Outputs CPU + registers Auxiliary Storage Primary Memory Cache Inputs Hard disks, floppy disks, CD-ROMs, tape,... …lies between

COMP 4—Power Tools for the Mind 9 What’s in the box? Physical organization: (can be “on-chip” and/or off-chip) On-chip cacheOff-chip cache

COMP 4—Power Tools for the Mind 10 What’s in the box? 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.) 11

COMP 4—Power Tools for the Mind 11 What’s in the box? Other architectural designs that affect speed: –We won’t discuss here….JUST FOR CULTURE 12 –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 12 What’s in the box? 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 13 What’s in the box? More about physical components Transistor : elementary building block. –Solid-state switch—can switch states in less than 20 nanoseconds. Less than 1 micron wide! ( microns) Gate Drain Source “Semi-Conductor” Gate Drain Source CHANNEL SILICON SUBSTRATE

COMP 4—Power Tools for the Mind 14 What’s in the box? 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 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 15

COMP 4—Power Tools for the Mind 15 What’s in the box? Individual transistors— Newer generation microprocessors (high end:.18-micron wide transistors, >42 million transistors/chip. Circuit board Bus (commun. Channels) Pins: connectors that allow communications with other chips. Plug into circuit board socket. Package 16 The Chip

COMP 4—Power Tools for the Mind 16 What’s in the box? System board Expansion slot/card or board/port: –NOTE: I will not expect you to memorize all the types of expansion slots, cables, connectors, and ports! Just understand what each is for (a slot, cable, a port….) Device driver Graphics card Printers GOOD textbook coverage: --Chapter 2 pages 62 thru Chap 2 pages 88 thru 96 So we WON’T COVER HERE…. Digital Electronics; and Input and Output devices 18

COMP 4—Power Tools for the Mind 17 What’s in the box? You should understand the jargon better. Example (part of an advertisement in 2005): –Dell Dimension 4700 Processor: Intel Pentium 4 with 2.8 GHz processor Memory: 256 MB (to 2 GB) SDRAM at 400 MHz Storage: Ultra Hard drives up to 200 GB Drive bay options: Dual optical drive bays with your choice of DVD-ROM, CD-RW/DVD or CD-RW/DVD-RW combo Ports: 6 USB 2.0 ports (2 front & 4 back), one serial port and one parallel port. –Front: digital camera, MP3 player, … –Back: printer, scanner… Monitors: Up to 21” (19.8” viewable) CRT displays and 19” Flat Panel (19” viewable) displays Video graphics: …… and Ultra 8X AGP graphics available Sound: Premium sound cards and brand-name speakers… Software: pre-loaded with Microsoft Windows XP operating system. Plus you can choose from Corel Works or Microsoft Office XP professional or small bus ed. Processor Cache: 1 MB (SRAM) Modem/Network: 56 KB/s or 100Mbit/s Service and support options…. 19