1976435213 - Computer Organization CDA 3103 Dr. Hassan...

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Unformatted text preview: Computer Organization CDA 3103 Dr. Hassan Foroosh Dept. of Computer Science UCF Copyright Hassan Foroosh 2004 Computer System Organization Processor Computer Control Datapath Memory Devices Input Output Note: Lectures first introduce conceptual framework, then application. Textbook presents in the other order. Overview of Lecture Basics Why use a memory hierarchy? Memory technologies: SRAM and DRAM Principle of locality Caches Mapping, blocks, write policy, replacement, performance Application Beyond Memory Hierarchy Cache techniques are applied throughout computer systems Memory cache Virtual memory Translation Buffers Branch prediction Disk cache Distributed file system cache Browser cache Proxy cache So, even if you never design processor or memory system hardware, it is important to understand cache principles and techniques Memory Technologies Random access technologies Random => access time (approx) same for all locations SRAM: Static Random Access Memory 4 or 6 transistors per bit Fast, but low density, high power, expensive Static => internal feedback maintains data while power is on DRAM: Dynamic Random Access Memory 1 transistor per bit Inexpensive, high density, low power, but slow (2-100X SRAM) Dynamic => need to be refreshed regularly to maintain data Memory Technologies Not-so-random access technologies Access time varies by location at any time Common technologies mechanically move a magnetic or optical (not electronic) recording medium past sensors Examples: magnetic disk, magnetic tape, optical CD Higher density and lower cost than RAM, but slow (10 5 10 8 X DRAM) Non-volatile => maintain data without power Typical hierarchy includes SRAM, DRAM, disk The Goal Illusion of large, fast, cheap memory Fact: Large memories are slow, fast memories are small How do we create a memory that is large, cheap and fast (most of the time)? Hierarchy Parallelism Who Cares About the Memory Hierarchy? Proc 60%/yr. (2X/1.5yr) DRAM 9%/yr. (2X/10 yrs) 1 10 100 1000 1980 1981 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 DRAM CPU 1982 Processor-Memory Performance Gap: (grows 50% / year) Performance Time Moores Law Processor-DRAM Memory Gap (latency) Technology Trends Capacity Speed (latency) Logic 4x in 3 years 2x in 3 years DRAM 4x in 3 years 2x in 15 years Disk 4x in 3 years 2x in 10 years DRAM Year Size Cycle Time 1980 64 Kb 250 ns 1983 256 Kb 220 ns 1986 1 Mb 190 ns 1989 4 Mb 165 ns 1992 16 Mb 145 ns 1995 64 Mb 120 ns 1000X 2X...
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1976435213 - Computer Organization CDA 3103 Dr. Hassan...

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