 Computer memory is device that is used to store data or programs (sequences of instructions) on a temporary or permanent basis for use in an electronic digital computer.  Computer memory is divided into two categories: 1.ROM (Non volatile) 2.RAM (Volatile) 1Powered by DeSiaMore

 ROM, consists of memory chips that contain programs that are acid-burned into the chips at the factory. The programs on a ROM chip (sometimes called firmware) are permanent; they cannot be changed.  ROM stores system BIOS and startup BIOS programs in a microchip that does not lose data when the power is turned off. 2Powered by DeSiaMore

 Flash ROM can be used on systemboards, and it allows upgraded versions of the BIOS to be written to it without having to physically replace the chip.  Technically speaking, Flash ROM is called EEPROM (electronically erasable programmable read-only memory), which means you can change the programming on the chip through software on your PC.  The updated programming will be retained, even when you turn off your PC for long periods of time, until you change it again. 3Powered by DeSiaMore

 BE VERY CAREFUL that you upgrade the BIOS with the correct upgrade.  Upgrading with the wrong file could make your system BIOS totally useless.  If you’re not sure that you’re using the correct upgrade, DON’T GUESS.  Check with the technical support for your BIOS before moving forward.  To upgrade Flash ROM, follow the directions that came with your systemboard and the upgrade software itself. 4Powered by DeSiaMore

 RAM, can be written to and read from by the CPU and some applications.  It is stored on chips that are either socketed or soldered directly on the systemboard or housed on little mini-boards.  Since RAM depends on power from the computer, all of the data in RAM is lost when the power is turned off. 5Powered by DeSiaMore

 RAM is a volatile memory.  For economic reasons, the main memories found in personal computers are normally consists of dynamic RAM (DRAM).  Other parts of the computer, such as cache memories and data buffers in hard disks, normally use static RAM (SRAM). 6Powered by DeSiaMore

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 DRAM (memory) modules Single In-line Memory Module (SIMM) Dual In-line Memory Module (DIMM)  Double Data Rate (DDR)  (Synchronous DRAM) SDRAM modules operate at various speeds, depending on the bus speed whereas SIMM module only operates at a single speed. 9Powered by DeSiaMore

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 When installing SIMMs or DIMMs, remember to protect the chips against static electricity.  Always use a ground bracelet as you work.  Turn the power off and remove the cover to the case.  Handle memory modules with care. Ground yourself before unpacking or picking up a card.  Don’t stack cards, because you can loosen a chip. 11Powered by DeSiaMore

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 Place each module securely in its slot. Turn on the PC and watch the amount of memory being counted by POST during the boot process.  If all the memory you expect does not count up correctly, remove and reseat each module carefully.  To remove a module, release the latches on both sides of the module and gently rotate the module out of the socket at a 45-degree angle. 13Powered by DeSiaMore

 When you add more memory to a computer, ask yourself these questions:  How much memory do I need?  How much memory can my computer physically accommodate?  What increments of memory does my systemboard support?  How much additional memory is cost effective?  What kind of memory can fit on my systemboard? 14Powered by DeSiaMore

 What memory is compatible with the memory I already have installed?  Adding more memory to improve a slow- performing PC will probably not help. Perhaps what you might really need is a more powerful CPU, or a faster hard drive or systemboard.  Therefore it is imperative to observe your options before rushing to increase memory. 15Powered by DeSiaMore

 Memory can be viewed as both physical memory installed on the systemboard and expansion boards, as well as logical memory managed by the operating system.  Two kinds of physical memory are RAM and ROM.  System BIOS is stored on ROM chips on the systemboard. In addition, expansion boards sometimes have ROM chips on them, holding BIOS programming to manage the device.  Two kinds of memory modules are SIMMs and DIMMs. 16Powered by DeSiaMore

 There are two kinds of RAM: SRAM and DRAM. SRAM is faster because it holds data as long as power is available to the chip. DRAM loses the data after a very short time and must be refreshed.  SRAM is used in a memory cache, which speeds up the overall computer performance by temporarily holding data and programming that may possibly be used by the CPU in the near future.  Flash memory holds data permanently until it is overwritten, and is commonly used on Flash ROM chips and memory cards for notebook computers. 17Powered by DeSiaMore

 Synchronous DRAM is a faster kind of memory than the less expensive asynchronous DRAM found on SIMMs.  SRAM comes as either synchronous or asynchronous memory. Synchronous is faster and slightly more expensive than asynchronous memory.  The practice of copying BIOS from slower ROM chips to faster RAM chips for processing is called shadowing ROM. The area of RAM holding the BIOS is called shadow RAM. 18Powered by DeSiaMore

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 A computer power supply changes and conditions the house electrical current in several ways, functioning as both a transformer and a rectifier.  It steps down the voltage from the 220 Volt house current to 3.3, 5, and 12 volts or to 5 and 12 volts, and changes incoming alternating current to direct current, which the computer and its peripherals require.  The monitor, however, receives the full 220 volts of AC current, converting that current to DC. 20Powered by DeSiaMore