Transcript Computers: Tools for an Information Age

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
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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
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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
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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
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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?
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Processor trends
• The numbers of transistors in a CPU
• Word size
• Frequency
• Number of processors on a chip
• Voltage
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Factors of system performance
• CPU speed
• Memory size
• Front bus speed
• Access speed to storage
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Storage hierarchy
• Register
• Cache
• Main memory
• Secondary storage, such hard drive
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Cache
Memory
• A temporary storage
area
Cache L2
– Speeds up data
transfer within computer
• Processor cache
Cache L1
Control Unit
Registers
ALU
CPU
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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
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