Types of RAM

Latest PCs use 2 types of RAMs.

       I.      Dynamic RAM (DRAM)

On Dynamic RAM data stores in a very small amount of time such as a fraction of a second.  The data disappear within very short period of time.  It is necessary to refresh the date stores every time.  Comparatively very cheaper.

    II.      Static RAM (SRAM)

Data will be stored as far as the electricity power is available.  The fastest compared to other memory type. But the price and the power consumption is very high.

Type	Speed	Density	Cost
DRAM	Slow	High	Low
SRAM	Fast	Low	High

Main Memory & DRAM

DRAM is used for the Main Memory of a PC.  Capacity of DRAM is comparative high.  Available form 32 MB to 2 GB.  In near future we will be able to take about the DRAM/memory capacities in 10 GB or its multiplications.

Cache Memory

The cache memory is very important to the PC system and its speed. Cache sits on newer processor as L1 (level 1) memory and as L2 memory. This allows kind of a buffer for the CPU. The CPU (Central Processing Unit) is faster than the rest of the system in most cases and needs a place to store information that can be accessed fast, this is where L1 and L2 come in. The cache minimizes the number of outgoing transactions from the CPU, it sends and receives information from the system memory and passes it to the CPU so the CPU can do more of its work internally thus speeding overall pc performance.

CPU

Cache

System Memory

The cache itself is made up of extremely fast silicon memory, and is called SRAM (Static RAM). This is a super fast RAM and is not very cheap.

Memory – Presentation to the Market

There are several ways of introducing and presenting memories to the market.

1.      SIMM – (Single Inline Memory Module)

This made assembling number of separate DRAM DIP Chips on a small Circuit Board.  This card (Small Circuit Board) is fixed into a socket on the Mother Board.  SIMM was issued in 2 main form factors.

01.I      30 Pin SIMM  -  Mostly used in 386 mother boards. Sometimes used in 286 and 486 Motherboards also.  As these are very slow these are not used in nowadays computer.  But still can be seen used in Laser Printers.

01.II     72 Pin SIMM - Used mostly in 486, Pentium and sometimes in 386 Motherboards.  Before the introduction of DIMM used in Pentiums also.  Can be rarely found in today’s computers also.  Still used in Laser Printers.

                               

2.      SD RAM/DIMM – Duel Inline Memory Module

This has connectors in both sides.  Commonly used DIMMs have 168 Pins.  But 100 Pins and 144 Pins are also available.  Only issued in SDRAM and EDO modes. PC 66, PC 100 and PC 133 are available.