11-memory - 1 Memory System Design Computer Systems Design...

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1 Computer Systems Design and Architecture by V. Heuring and H. Jordan © 1997 V. Heuring and H. Jordan Memory System Design
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2 Computer Systems Design and Architecture by V. Heuring and H. Jordan © 1997 V. Heuring and H. Jordan Compo- nent Access Random Random Random Direct Sequential Capa- 64-1024 8KB-4MB 64MB-2GB 10-200GB 1TB city, bytes Latency 0.4-10ns 0.4-20ns 10-50ns 10ms 10ms-10s Block 1 word 16 words 16 words 4KB 4KB size Band- System 80MB/s 10-4000MB/s 50MB/s 1MB/s width clock Rate Cost/MB High $10 $0.25 $0.002 $0.01 The Memory Hierarchy, Cost, and Performance CPU Cache Main Memory Disk Memory Tape Memory Some Typical Values:
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3 Computer Systems Design and Architecture by V. Heuring and H. Jordan © 1997 V. Heuring and H. Jordan Problems in High-Performance Computing Systems Processor much faster than Main Memory Solution: Insert fast Cache memory between Processor and Main Memory Amount of Main Memory available in a machine varies; program/data might not fit into memory Program contains hard-coded addresses; how to move a program to a different memory location? Processor can only address up to 4 GB; how to connect a 1 TB disk to system? Solution: Virtual Memory hides details of memory hierarchy providing the illusion of a flat address space
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4 Computer Systems Design and Architecture by V. Heuring and H. Jordan © 1997 V. Heuring and H. Jordan Cache Design Processor much faster than Main Memory Solution: Insert fast Cache memory between Processor and Main Memory
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5 Computer Systems Design and Architecture by V. Heuring and H. Jordan © 1997 V. Heuring and H. Jordan Considering any two adjacent levels of the memory hierarchy Some definitions: Temporal locality : the property of most programs that if a given memory location is referenced, it is likely to be referenced again, “soon.” Spatial locality : if a given memory location is referenced, those locations near it numerically are likely to be referenced “soon.” Working set : The set of memory locations referenced over a fixed period of time, or in a time window . Notice that temporal and spatial locality both work to assure that the contents of the working set change only slowly over execution time. CPU Primary level Secondary level • • • • • • two adjacent levels in the hierarchy Faster, smaller Slower, larger Defining the Primary and Secondary levels:
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6 Computer Systems Design and Architecture by V. Heuring and H. Jordan © 1997 V. Heuring and H. Jordan Primary and secondary levels of the memory hierarchy Primary level Secondary level The item of commerce between any two levels is the block . Blocks may/will differ in size at different levels in the hierarchy. Example: Cache block size ~ 16-64 bytes . Disk block size: ~ 1-4 Kbytes . As working set changes, blocks are moved back/forth through the hierarchy to satisfy memory access requests.
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11-memory - 1 Memory System Design Computer Systems Design...

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