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EET 450 - Advanced Digital

EET 450 - Advanced Digital. Chapter 4 Computer Memory. Memory. Primary and Secondary Storage Primary is part of main memory at one point, DISK, DRUM, or CORE memory was used. Secondary is an antiquated view of a system, but usually refers to mass storage.

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EET 450 - Advanced Digital

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  1. EET 450 - Advanced Digital Chapter 4 Computer Memory

  2. Memory • Primary and Secondary Storage • Primary is part of main memory • at one point, DISK, DRUM, or CORE memory was used. • Secondary is an antiquated view of a system, but usually refers to mass storage. • Old technology included the use of punch card, tape or DISK/DRUM memory

  3. Memory • Main memory in modern PC’s uses a volatile type of memory • Semiconductor memory is the rule • Non-Volatile memory is used for special purpose functions within the PC • BIOS • CMOS - is battery backup version on non-volatile memory • EEPROM or FLASH memory

  4. Measurement • Capacity of memory is based on the amount of digital information that can be stored. • Bits/ Bytes/ Nibbles • Words • Double Words • Quad Words • Line

  5. Memory is used in modern computers is based on GRANULARITY • the smallest amount of memory that can be addressed • Increased bus widths have INCREASED the size of the smallest granule accessed • Pentium/Pentium Pro use eight-byte modules

  6. Technologies • Random Access Memory • Dynamic Memory Data In Data Out

  7. Static Memory - referred to as SRAM • Read Only Memory ROM • Mask ROM - older bios chips • PROM - Programmable • EPROM - Erasable Programmable ROM • EEPROM - Electrically Erasable PROM • Flash Memory

  8. Where’s the Memory • Memory uses in a PC L1 L2 C A C H E C A C H E Main Memory CPU Mass Storage Cache

  9. Memory Use • Storage of program information • Storage of BOOT information • program and settings • Storage of DATA

  10. Logical Organization • Real Mode Memory - • legacy of the 8086 processor • 1 Mbyte address space • base memory

  11. Logical Organization • Protected Mode memory • Provides the entire address space of the processor • 4 Gbytes + • Lower Memory • Legacy stuff again • < 640k - conventional DOS memory

  12. BIOS Data Area • Vector Table - lower 1k • Upper Memory • the upper 384k of memory address space • top 32K - ROM Bios memory

  13. High Memory • 64kB+16 bytes above Upper memory • address line A20 allows this • a function of binary round-off • Frame Buffer memory • Part of video memory

  14. Shadow Memory • Provides solution to slower ROM memory providing BIOS functions. • ROM memory is slower than fast RAM for a variety of reasons - bus width, intrinsic speed, etc. • BIOS is ‘shadowed’ into RAM at boot time, allowing faster access to these functions. • Other ROM memory - controller cards, video, etc may be shadowed.

  15. Cache Memory • provides the speed interface between slower memory/devices and the faster memory/devices

  16. System Resource Memory • Memory allocated by ‘heaps’ • older OS problems with release of memory on program exit.

  17. Unified Memory Architecture • UMA • maps main memory into video display address space

  18. Performance • Memory Speed • based on access speed of integrated circuits • -12 is 120 nS memory, • Must have faster memory than called for by processor speed. • Bus interface may be the problem.

  19. Caching • Cache Size - 1k • 256 k most favored • Note: Celeron processor suffered severe performance penalties by failing to include Cache memory

  20. Cache Performance • four sections • show cache hits for access to store a single line - one for each transfer • 1-1-1-1 would be best

  21. Cache Mapping • Direct Mapped • CACHE mapped to block of memory • Full associative • CACHE can be for any block of memory • very costly - complex • set-associative • sections of CACHE are direct mapped.

  22. Burst-Mode Caches • blocks of data at a time • Synchronous Burst Ram - SRAM (note acronym conflict) • Pipelined burst SRAM

  23. Cache consistency • Write-through • Write-back

  24. Memory Types • Static Column Ram • Page-Mode RAM (FP) • Extended Data Out Memory (EDO) • Burst EDO DRAM • Synchronous DRAM • Enhanced DRAM • Cached DRAM

  25. Rambus DRAM • Multibank DRAM • PC100 RAM • PC166/266/333/400 etc.

  26. Memory Packages • DIP • SIPP • SIMM • 30 pin • 72 pin • DIMM • 168 pin

  27. Assignment • Complete Chapter on memory • Review ‘Tom’s Hardware Guide: Ram Guide. • Research ‘other’ RAM packages that may be available.

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