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Computers8 Ch4 3


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Chapter 4 - Part III

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Computers8 Ch4 3

  1. 1. Chapter 4 B.M.H The Central Process Unit
  2. 2. Learning Objectives <ul><li>List the measures of computer processing speed and explain the approaches that increase speed. </li></ul><ul><ul><li>Microprocessor speed </li></ul></ul><ul><ul><li>Memory cache </li></ul></ul><ul><ul><li>Flash memory </li></ul></ul><ul><ul><li>RISC computers </li></ul></ul><ul><ul><li>Parallel processing </li></ul></ul>MIU P4-116
  3. 3. What makes a computer fast? <ul><li>Factors </li></ul><ul><ul><li>Microprocessor speed </li></ul></ul><ul><ul><li>Bus line size </li></ul></ul><ul><ul><li>Availability of cache </li></ul></ul><ul><ul><li>( More sophisticated ones ) </li></ul></ul><ul><ul><li>Flash memory </li></ul></ul><ul><ul><li>RISC computers </li></ul></ul><ul><ul><li>Parallel processing </li></ul></ul>MIU
  4. 4. Computer processing speeds <ul><li>The execution of an instruction </li></ul><ul><ul><ul><li>may be measured in </li></ul></ul></ul><ul><ul><li>Millisecond : 1/10 3 of a second </li></ul></ul><ul><ul><ul><li>very slow (old) computer </li></ul></ul></ul><ul><ul><li>Microsecond : 1/10 6 of a second </li></ul></ul><ul><ul><li>Nanosecond : 1/10 9 of a second </li></ul></ul><ul><ul><ul><li>modern computer </li></ul></ul></ul><ul><ul><li>Picosecond : 1/10 12 of a second </li></ul></ul>MIU
  5. 5. Computer processing speeds <ul><li>Microprocessor speeds </li></ul><ul><ul><li>are determined by </li></ul></ul><ul><ul><li>Microprocessor ’ s clock speed </li></ul></ul><ul><ul><li>MIPS </li></ul></ul><ul><ul><li>Megaflop </li></ul></ul>MIU
  6. 6. Microprocessor ’ s clock speed <ul><li>Usually expressed in </li></ul><ul><ul><li>megahertz (MHz) </li></ul></ul><ul><ul><ul><li>10 6 of machine cycles per second </li></ul></ul></ul><ul><ul><li>gigahertz (GHz) </li></ul></ul><ul><ul><ul><li>10 9 of machine cycles per second </li></ul></ul></ul><ul><ul><li>Ex. a PC listed at 500MHz </li></ul></ul><ul><ul><ul><li>: capable of handling 500*10 6 machine cycles/s </li></ul></ul></ul><ul><li> Direct comparison of clock speeds </li></ul><ul><ul><li>Meaningful only between identical microprocessors </li></ul></ul>MIU
  7. 7. MIPS <ul><li>One m illion i nstructions p er s econd </li></ul><ul><ul><li>Ex. A computer with speed of 0.5MIPS </li></ul></ul><ul><ul><li>: execute 500,000 instructions per second </li></ul></ul><ul><ul><li>High-speed personal computer </li></ul></ul><ul><ul><li>: perform at 100 MIPS and higher. </li></ul></ul><ul><li>A more accurate measure than clock speed </li></ul>MIU
  8. 8. Megaflop <ul><li>One m illion flo ating- p oint operation per second </li></ul><ul><li>The ability of the computer to perform complex mathematical operation. </li></ul>MIU
  9. 9. Cache <ul><li>Temporary storage area </li></ul><ul><ul><li>Designed to speed up data transfer within the computer </li></ul></ul><ul><li>Types </li></ul><ul><ul><li>Memory cache </li></ul></ul><ul><ul><li>Disk cache ; chapter 6 </li></ul></ul>MIU
  10. 10. Memory cache <ul><li>A relatively small block of very fast memory </li></ul><ul><ul><li>Designed for the specific purpose of speeding up the internal transfer of data and software instructions. </li></ul></ul><ul><ul><li>The data and instructions stored in cache </li></ul></ul><ul><ul><li>: are most recently or most frequently used. </li></ul></ul><ul><li>Types </li></ul><ul><ul><li>Internal cache </li></ul></ul><ul><ul><li>External cache </li></ul></ul>MIU
  11. 11. Memory cache MIU
  12. 12. Memory cache <ul><li>Internal cache, Level 1 (L1) cache </li></ul><ul><ul><li>In the processor </li></ul></ul><ul><ul><li>The fastest sort </li></ul></ul><ul><ul><li>Takes up precious space and increase the cost of the microprocessor </li></ul></ul><ul><ul><li>No more than 128KB </li></ul></ul><ul><li>External cache, Level 2 (L2) cache </li></ul><ul><ul><li>On separate chips </li></ul></ul><ul><ul><li>Probably 256KB or 512KB </li></ul></ul><ul><ul><li>SRAM technology </li></ul></ul><ul><ul><li>Cheaper and slower than L1 cache </li></ul></ul><ul><ul><li>much faster (and more expensive) than memory </li></ul></ul>MIU
  13. 13. Flash Memory <ul><li> Memory : volatile </li></ul><ul><li> Secondary storage : slow rate </li></ul><ul><li>Flash memory </li></ul><ul><ul><li>nonvolatile RAM </li></ul></ul><ul><ul><li>Faster than secondary storage </li></ul></ul><ul><ul><ul><li>Used in cellular phones, digital cameras, and digital music recorders </li></ul></ul></ul><ul><ul><ul><li>Replacing disks in some handheld computers </li></ul></ul></ul><ul><ul><ul><li>Being produced in credit card </li></ul></ul></ul><ul><ul><ul><li>Smaller than a disk drive </li></ul></ul></ul><ul><ul><ul><li>Require only half the power </li></ul></ul></ul>MIU
  14. 14. RISC Technology <ul><li>Instruction set </li></ul><ul><ul><li>a specific group of instructions that each type of CPU is designed to understand </li></ul></ul><ul><ul><ul><li>such as ADD or MOVE </li></ul></ul></ul><ul><ul><li>A single program instruction </li></ul></ul><ul><ul><ul><li>May be made up of a substantial number of subinstructions, each of which must take at least one machine cycle </li></ul></ul></ul><ul><li>Instructions set computing types </li></ul><ul><ul><li>CISC ( Complex instruction set computing ) </li></ul></ul><ul><ul><li>RISC ( Reduced instruction set computing ) </li></ul></ul>MIU
  15. 15. RISC Technology <ul><li>CISC ( Complex instruction set computing) </li></ul><ul><ul><li>Many of the most complex instructions in the instruction set are rarely used </li></ul></ul><ul><ul><ul><li>A problem to speedy performance </li></ul></ul></ul><ul><ul><li>Intel ’ s Pentium family </li></ul></ul><ul><li>RISC ( Reduced instruction set computing) </li></ul><ul><ul><li>Small subset of instructions </li></ul></ul><ul><ul><li>Increase the speed </li></ul></ul><ul><ul><li>Programs in graphics and engineering areas </li></ul></ul><ul><ul><ul><li>A significant performance advantage </li></ul></ul></ul><ul><ul><li>PowerPCs and Alphas </li></ul></ul>MIU
  16. 16. Parallel Processing <ul><li>Serial processing </li></ul><ul><ul><li>The execution of one instruction at a time </li></ul></ul><ul><li>Pipelining </li></ul><ul><ul><li>An instruction action doesn ’ t need to be completed before the next instruction action is begun. </li></ul></ul><ul><ul><ul><li>An instruction : One fetch is complete for it and it moves to decode. </li></ul></ul></ul><ul><ul><ul><li>the next instruction : Fetch is begun for the next. </li></ul></ul></ul><ul><ul><li> Problem : a single electronic pathway (bus line) acts like a bottle neck. </li></ul></ul>MIU
  17. 17. MIU
  18. 18. Parallel Processing <ul><li>A method of using multiple processors at the same time </li></ul><ul><ul><li>Many processor, each with its own memory unit, working at the same time </li></ul></ul><ul><li>Ultimate speed solution </li></ul><ul><li>Capable of operating in term of teraflops </li></ul><ul><ul><li>Trillions of floating-point instruction per second </li></ul></ul><ul><ul><ul><li>Network server : with 4 to 16 processors </li></ul></ul></ul><ul><ul><ul><li>Supercomputer : with 100 or 1000 processors </li></ul></ul></ul>MIU