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Higher Computing. Computer Systems 3. Computer Performance. MIPS . Millions of Instructions Per Second These are machine code (low level instructions. The types of instructions are not specified. Only useful if all test conditions are the same. MIPS continued. Wikipedia says:
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Higher Computing Computer Systems 3. Computer Performance
MIPS • Millions of Instructions Per Second • These are machine code (low level instructions. • The types of instructions are not specified. • Only useful if all test conditions are the same.
MIPS continued • Wikipedia says: • Critics of the term refer to it as "Meaningless Indication of Processor Speed“ • MIPS are certainly not comparable between CPU architectures. • See table for MIPS performance down the years. • Remember: All improvements have a cost. When deciding how to improve a system the ratio of cost to best performance will always be considered.
Clock Speed • The clock is controlled by an internal crystal and pulses at a regular rate. • All activities start on the pulse of the clock. • Cycle time- the time between pulses. • Not reliable – some instructions take several cycles and some computers can perform several tasks per cycle.
FLOPS • Floating Point Operations Per Second • Measures arithmetical calculation speed. • More reliable than MIPS. • A supercomputer is defined as a computer that operates at 1 or more gigaFLOPS.
Application-based Tests • Used to test both system and software performance. • Allows comparison of different systems by using benchmark tests. • See Scholar 3.2.2 • Examples of benchmark tests include: • Dhrystone Test • Whetstone Test • MemStone Test. • Investigate these tests.
Application-based Tests • When reviewing products, reviews use benchmark tests. • See http://www.pcpro.co.uk/labs/
Factors Effecting Performance • Data Bus Width • The wider the data bus, the greater the word size. • Investigate data bus widths on current PCs. • What effect would adding a wire have to the data bus?
Factors Effecting Performance • Use of Cache Memory • Cache is connected to the processor by its own bus that is wider than the data bus. • Cache memory is made up of SRAM.
Factors Effecting Performance • Data Transfer to and from Peripherals • Depends on the interface. • Task: • Find the data transfer rates of the following interfaces: • USB1 • USB2 • Firewire • Note: using a faster interface with a peripheral designed for an older one will not improve performance.
Factors Effecting Performance • Add more Main Memory • Virtual Memory – use of fast access backing storage to behave like RAM. Much slower than using actual RAM. • Most computers do not come with as much memory as it is possible to address. This is because: • Costs of computer manufacture is reduced • Applications rarely need the maximum amount of RAM to run. • Some memory locations that need to be addressed are in ROM.
Factors Effecting Performance • Increase VRAM • Increase Clock Speed • Add more processors • This allows for parallel processing where several processors share tasks enabling them to be completed quicker. • Increase address bus width. • What effect does this have on total addressable memory?
Current Trends in Hardware • TASK: • Compare the clock speeds, RAM size and backing storage capacity of similarly priced PC’s from now and from 1, 2 and 5 years ago. • Use PC Pro magazines. • Complete questions on question sheet.
