W6Lect - Memory 1 Main Memory (RAM) Is the part of the...

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1 Memory
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2 Main Memory (RAM) Is the part of the computer where data may be stored and retrieved. It provides the workspace for the CPU. Without it, the computer could not function. It relies on microchips, currently integrated into modular “sticks” called DIMMs. Adding more memory can greatly improve performance, up to limits determined by other factors. The speed of modern memory types is synchronized with CPU speeds, so that no buffering is required and no “bottleneck” occurs.
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3 Categories of Memory A typical computer employs several types of memory “Physical Memory” or RAM must be distinguished from “Virtual Memory” which is a memory type that borrows hard-drive space to extend the apparent size of physical memory. Memory may also be classed as Primary or Secondary
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4 Categories of Memory cont’d… The memory types employed by a typical modern PC may be viewed as a hierarchy, with smaller, faster and more expensive memory types at the top supplemented by larger, slower and less expensive types as we move lower. When properly implemented, we enjoy the benefits of high performance without the expense.
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5 Memory Hierarchy Source: HowStuffWorks.com Primary Secondary
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6 Physical Memory Preview Temporarily holds data and instructions as CPU processes them. Two categories ROM Retains its data RAM Static RAM (SRAM) Dynamic RAM (DRAM) Loses its data Housed on SIMMs, DIMMs, or RIMMs
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7 ROM on the Motherboard Originally memory chips that contained programs (ROM BIOS) acid-etched into the chips and is Non changeable EPROM (erasable programmable ROM) and EEPROM (electrically erasable programmable ROM) chips can be reprogrammed
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8
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9 SIM RAM module Volatile! Originally speed of RAM measured in nanoseconds (billionths of a second) Banks of 8 or 9 chips measured in bits e.g. 64Kbits Either individual chips or modules Parity determines number of chips RAM Bank on motherboard
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10 RAM on the Motherboard Two categories Dynamic RAM (DRAM) Needs to be refreshed constantly by the memory controller Usually stored on DIMMs, less commonly on RIMMs Static RAM (SRAM) Serves as main memory Provides a memory cache
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11 RAM on the Motherboard
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12 DRAM Technologies
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SRAM (Static RAM) Faster than DRAM and capable of keeping pace with today’s CPU’s. as fast as 7-9 nanoseconds and 2 or less for ultrafast SRAM). SRAM’s design calls for a cluster of six transistors for each bit of storage. Eliminates need for refreshing. Used for cache memory. Used for CMOS (NVRAM) a trickle of electricity required to retain the data Some comes in burst-mode format (has its own clock), making it suitable for the PowerPC CPU’s. In credit-card memory (in 128K, 256K, 512K, 1MB, 2MB and 4MB sizes) with
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This note was uploaded on 04/14/2011 for the course HWD 101 taught by Professor Brain during the Spring '11 term at Seneca.

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W6Lect - Memory 1 Main Memory (RAM) Is the part of the...

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