1 Microprocessor speeds Measure of system clock speed –How many electronic pulses the clock produces per second (clock frequency) –Usually expressed in frequency (unit Hz) 1 Hz = 1 cycle / second Kilohertz (KHz), Megahertz (MHz), Gigahertz (GHz) –Or how much time for each cycle: clock cycle time clock cycle time = 1 / clock frequency Second, millisecond, microsecond, nanosecond Comparison of clock speed only meaningful between identical microprocessors

2 Other performance measures Millions of Instructions per Second (MIPS) –High-speed personal computers can perform over 500 MIPS –Typically a more accurate measure of performance than clock speed Megaflop: one million floating-point operations –Measures ability of computer to perform complex mathematical operations

3 Types of microprocessors Microprocessor Intel makes a family of processors –Pentium III and Pentium4 processors in most PCs –Celeron processor sold for low-cost PCs –Xeon and Itanium for high-end workstations and network servers Other processors –AMD make Intel-compatible microprocessors –PowerPC chips used primarily in Macintosh computers –Compaq’s Alpha microprocessor used in high-end servers

4 Factors to CPU performance Size of word Larger word mean more information can be processed by each instruction Fast system frequency means more instructions can be done in a unit of time or equivalently short clock cycle time means each instruction can be done an short time Small number of clock cycles for each instruction more instruction can be done in a unit time Power consumption

5 Silicon technology The size of a transistor –New technology makes the size of a transistor smaller and smaller! –Unit used to measure the size –Majority: 0.13 micro meter or 130 nano meter Moving to 0.09 micro meter or 90 nano meter Advanced: 65 nano meters Next a year: 45 nano meters Limit 10 nano meter?

6 Processor trends The numbers of transistors in a CPU Word size Frequency Number of processors on a chip Voltage

7 Factors of system performance CPU speed Memory size Front bus speed Access speed to storage

8 Storage hierarchy Register Cache Main memory Secondary storage, such hard drive

9 Cache A temporary storage area –Speeds up data transfer within computer Processor cache Control Unit ALU Registers Memory CPU Cache L1 Cache L2

10 Processor cache A small block of high-speed memory –Stores most frequently and most recently used data and instructions Microprocessor looks for what it needs in cache first –Transferred from cache much faster than from memory –If not in cache, control unit retrieves from memory The more cache “hits” the faster the system performance Internal (Level 1) cache built into microprocessor –Fastest access, but highest cost External (Level 2) cache on separate chip –Incorporated into processor on some current microprocessors