RAM

RAM (RANDOM ACCESS MEMORY)

RAM is used to temporarily store running or open programs.
There are two kinds of RAM

1) SRAM (Static RAM)
    - It is the fastest kind of RAM because it does not need to refresh.
    - Made up of transistor. (transistor store voltage)
    - Access time is 5 to 10ns (Nano Second)
2)DRAM (Dynamic RAM)
     - It is a bit slower than SRAM because it needs to refresh every few nano second.
     - Made up of capacitor. (capacitor store power)
     - Access time is 15 to 60ns.
     - Cheap
Note:- SRAM is used inside the processor. it is about 10 times more costly than DRAM.

Access Time-   Access time is taken by CPU (Central Processing Unit) to access memory locations of RAM is called access time. Incase of DRAM the access time will be more because it need to refresh time to time.

Types of RAM (DRAM)
1. EDORAM (Extended Data Out RAM)
  .It is a synchronous : meaning it will function individually without help of processor.
  . EDO RAM works by accessing large chunks(Blocks) of data to fide to the CPU. EDO RAM is asynchronous,means that it runs at a speed indeependent ot the system clock speed.
. EDO RAM comes in 72 pins SIMM's and 168 Pins DIMM's and has access time of 50 to 60ns.

2. SDRAM (Synchronous Dynamic RAM)
   . It is used very commonly.
   . it's speed ranges from
           i) PC66-66MHz
           ii) PC100-100MHz
           iii) PC133-133 MHz
  . SD RAM runs at the speed of system bus and has access time in 8 to 10 nano second range.
  . SD RAM speed measured in MHz because it operate the speed of system bus.
  . Most common types of SD RAM used of 168 Pin DIMM, 72 pin and 144 Pin SO DIMM'S and micro DIMM's.
  . speed of SO RAM =Speed of mother board.
  . Mostly used in PIII Mother Board.
              PIII- Mother Board speed is 133 MHz.
              PIV- Mother Board speed is above 400 MHz.