Memory

Random Access Memory Defined What is memory? operating system and other system software that control the usage of the computer equipment application programs that carry out a specific task data being processed by application programs  Three basic items stored in memory  Temporary storage place for data, instructions, and information  Consists of one or more chips on the motherboard or some other circuit board

Memory How is memory measured?  Size of memory is measured by the number of bytes available Kilobyte - 1,024 bytes Megabyte - one million bytes

Volatile Memory Loses its contents when the computer's power is turned off volatile memory Loses its contents when the computer's power is turned off Memory What are the two types of memory in the system unit? nonvolatile memory Does not lose its contents when the computer ’ s power is turned off

Memory Memory chips that can be read from and written to by the processor and other devices When the computer starts, operating system files are loaded from a hard disk into RAM What is random access memory (RAM)? As additional programs and data are requested, they also load from storage into RAM Most RAM is volatile

Storage (hard disk) RAM Step 3: When you quit Word, RAM may be used to store another program or data. The program is removed from the screen and the operating system ’ s user interface redisplays. Step 1: When your computer is running, certain operating system files are in RAM. Shown here is the operating system ’ s user interface. Step 2: When you start a word processing program such as Word, the program loads into RAM from a hard disk. As you create a document, it is in RAM and displays on your screen. Step 4: When you start a spreadsheet program such as Excel, the program loads into RAM from a hard disk. As you create a spreadsheet, it is in RAM and displays on your screen. Memory How are applications transferred in and out of RAM? Step 5: When you quit Excel, RAM may be used to store another program or data. Excel is removed from your screen and the operating system ’ s user interface redisplays.

Memory What is a memory module? single inline memory modules (SIMMs) Rambus ® inline memory module (RIMM)  Small circuit board with RAM chips, which are smaller in size than processor chips  Inserts into the motherboard  Three types: SIMMS, DIMMS, and RIMMS dual inline memory modules (DIMMs)

FPM-Fast Page Mode DRAM -traditional DRAM EDO-Extended Data Output -increases the Read cycle between Memory and the CPU SDRAM-Synchronous DRAM -synchronizes itself with the CPU bus and runs at higher clock speeds

RDRAM-Rambus DRAM -DRAM with a very high bandwidth (1.6 GBps) EDRAM-Enhanced DRAM -(dynamic or power-refreshed RAM) that includes a small amount of static RAM (SRAM) inside a larger amount of DRAM so that many memory accesses will be to the faster SRAM. EDRAM is sometimes used as L1 and L2 memory and, together with Enhanced Synchronous Dynamic DRAM, is known as cached DRAM.

SIMM vs. DIMM vs. RIMM? SIMM-Single In-line Memory Module DIMM-Dual In-line Memory Modules RIMM-Rambus In-line Memory Modules SIMMs offer a 32-bit data path while DIMMs offer a 64- bit data path. SIMMs have to be used in pairs on Pentiums and more recent processors RIMM is the one of the latest designs. Because of the fast data transfer rate of these modules, a heat spreader (aluminum plate covering) is used for each module

Memory What is a memory module? dual inline memory module (DIMM) memory chip  RAM chips usually reside on a small circuit board which inserts into motherboard

Memory What is read-only memory (ROM)? BIOS (basic input/output system) Stored on ROM Sequence of instructions the computer follows to load the operating system and other files when you first turn on the computer Nonvolatile — Contents not lost when the computer is turned off  Memory chips that contain data, instructions, or information that is recorded permanently Data can only be read, cannot be modified

Read Operation On a read the CPU will first try to find the data in the cache, if it is not there the cache will get updated from the main memory and then return the data to the CPU.

Write Operation On a write the CPU will write the information into the cache and the main memory.

Managing memory Use of memory software accelerator Assigning the memory page file Dumping memory Memory planning based on the possible program required loads

Common Memory Problems Terminal corrosion PCB Socket Broken PCB lines Defective memory chips Cold solder Burn component

Breaking Down the Memory Over heat Over voltage Overloading Incompatibility issue Wrong type of memory Defective motherboard Defective socket

Evolution of Memory 1970 RAM / DRAM 4.77 MHz 1987 FPM 20 MHz 1995 EDO 20 MHz 1997 PC66 SDRAM 66 MHz 1998 PC100 SDRAM100 MHz 1999 RDRAM 800 MHz 1999/2000 PC133 SDRAM133 MHz 2000DDR SDRAM 266 MHz 2001EDRAM450MHz

Memory Versus Storage What is storage? The media on which data, instructions, and information are kept, as well as the devices that record and retrieve these items

Memory Versus Storage How does storage differ from memory? When you want to work with a file, you remove it from storage and place it in memory When you are finished with the file, you remove it from memory and return it to storage Storage also called secondary storage, auxiliary storage, permanent storage, or mass storage Storage holds items such as data, instructions, and information for future use Storage is nonvolatile

Memory Versus Storage What is a storage medium and a storage device? storage medium The physical material on which a computer keeps data, instructions, and information storage device The computer hardware that records and retrieves items to and from a storage medium

Writing Process of transferring items from memory to a storage medium Serves as a source of output Memory Versus Storage What is reading and writing? Reading Process of transferring data, instructions, and information from a storage medium into memory Serves as a source of input

Memory Versus Storage What is access time? The amount of time it takes the device to locate an item on a disk Defines the speed of a disk storage device Memory (RAM) Compact Disc Floppy Disk Tape Hard Disk cost less expensive more expensive speed faster slower

Memory Versus Storage What is capacity? The number of bytes (characters) a storage medium can hold Manufacturers use many terms to define the capacity of storage media Storage Term Abbreviation Number of bytes Kilobyte Megabyte Gigabyte Terabyte Petabyte KB MB TB GB PB 1 thousand 1 million 1 billion 1 trillion 1 quadrillion

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