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EET 450 - Advanced Digital

This chapter delves into the intricacies of computer memory, focusing on primary and secondary storage systems. It outlines the evolution of memory types, including volatile (like DRAM) and non-volatile (like EEPROM and Flash) memory. Explore concepts like bus width, cache memory, and the significance of different RAM types in modern computers. The discussion also covers logical organization of memory, encompassing real and protected modes, the use of BIOS, and the emerging challenges in memory allocation and speed.

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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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