"What is RAM ? Your Computer Temporary Storage Info Page"

You maybe asking: What is RAM (Random Access Memory)?

Actually, RAM is a volatile memory that the computer uses to store program and data temporarily for execution. Volatile means that it is not permanent and can be change. It need power supply to keep the data stored in it.

All programs, instructions, and data must be stored in system memory (RAM) before the computer can use it. It will hold recently used programs, instructions, and data in memory if there is room. The more memory (capacity) in a PC, the more data can hold and the better your computer will perform.

If your computer doesn't have enough memory installed, its CPU must constantly retrieve data from permanent storage (hard disk). This method of data retrieval is slower than retrieving instructions and data from memory. In fact, if your PC doesn't have enough memory, some programs will run very slowly (or you might experience system crashes), and other programs won't run at all!

Here is the graphical illustration of a desktop RAM (left) and laptop RAM (right):

Computer RAM and laptop RAM

RAM Brand

There are a lot of brands, for example Kingston, Apacer, Corsair, Kingmax, etc. Most of the manufacturer offers life time warranty means that whenever the RAM manufacturers still produce the kind of RAM, the warranty is still valid.

RAM Capacity

Memory is measured in terms of bytes. One byte is equal to approximately one character in a word processing document. A unit equaling approximately one thousand bytes (1,024, to be exact) is called a kilobyte (KB), and a unit of approximately one thousand (1,024) kilobytes is called a megabyte (MB). A thousand megabytes is a gigabyte (GB).

The capacity of one piece of RAM ranges from 2 MB to 8 GB (8,000 MB) or whatever latest. Currently, most of the computers are using 512MB, 1 GB, 2 GB, or 4 GB of RAM.

Types of RAM

Before you buy new memory for your computer, it's essential to identify the type you need. The table below lists the RAM modules:

Name Number of Notches in Card Edge Connector Usage
30-pin SIMM (single inline memory module) One Desktop computers (most earlier 286, 386, 486, Pentium I)
72-pin SIMM One EDO RAM in desktop computers (mostly Pentium I)
168-pin DIMM (dual inline memory module) Two SDRAM in desktop computers (mostly Pentium II and III)
184-pin DIMM One DDR SDRAM in desktop computers
184-pin RIMM Two Rambus in desktop computers
240-pin DIMM One DDR2 SDRAM in desktop computers
240-pin DIMM One DDR3 SDRAM in desktop computers
144-pin SODIMM (small outline dual inline memory module) One Notebook computers
200-pin SODIMM One Notebook computers

Note: The 30-pin SIMM already obsolete.

Each memory modules come in a confusing number of different physical sizes, speeds, and other characteristics. Below shows the relative sizes, shapes, and speed of several module types.

1) Types of 72 pins RAM

EDO (Extended Data Output) - Access Speed: 50, 60, 70 nanoseconds
FPM (Fast Page Mode) - Access Speed: 50, 60, 70 nanoseconds

2) Types of 168 pins RAM

SDRAM (Synchronous Dynamic RAM)
Memory Speed (MHz) Max Bandwidth
PC 66 66 0.53 GB/second
PC 100 100 0.80 GB/second
PC 133 133 1.06 GB/second
PC 150 150 1.20 GB/second
PC 166 166 1.20 GB/second
E.g. PC 100: 8 bytes X 100 Mhz = 800 MBps/0.8GBps

3) Types of 184 pins RAM

DDR (Double Data Rate) SDRAM
Memory Speed (MHz) Max Bandwidth
PC2100 (DDR 266) 133 2.13 GB/second
PC2700 (DDR 333) 166 2.66 GB/second
PC3200 (DDR 400) 200 3.20 GB/second

Here are the graphical illustrations between DDR and DDR2 desktop RAM. You should notice the key notch positions of both types of RAM are in slightly different position.

Computer DDR and DDR2 desktop RAM

4) Types of 240 pins RAM

DDR2 (Double Data Rate 2) SDRAM

DDR2 400 MHz (PC2-3200)
DDR2 533 MHz (PC2-4200)
DDR2 667 MHz (PC2-5400)
DDR2 800 MHz (PC2-6400)
DDR2 900 MHz (PC2-7200)
DDR2 1000 MHz (PC2-8000)
DDR2 1066 MHz (PC2-8500)
DDR2 1150 MHz (PC2-9200)
DDR2 1200 MHz (PC2-9600)

DDR3 (Double Data Rate 3) SDRAM

DDR3 1066 MHz (PC3-8500)
DDR3 1333 MHz (PC3-10600/10666)
DDR3 1375 MHz (PC3-11000)
DDR3 1600 MHz (PC3-12800)
DDR3 1625 MHz (PC3-13000)
DDR3 1800 MHz (PC3-14400)
DDR3 1866 MHz (PC3-15000)
DDR3 2000 MHz (PC3-16000)

Here are the graphical illustrations between DDR2 and DDR3 desktop RAM:

Computer DDR2 and DDR3 desktop RAM

5) Types of 200 pins RAM

DDR PC2100 200-pin SODIMM (Small Outline DIMM)
DDR PC2700 200-pin SODIMM
DDR PC3200 200-pin SODIMM
DDR PC4200 200-pin SODIMM
DDR PC5300 200-pin SODIMM

As you can see, the RAM manufacturers is producing more and more advanced RAM in term of RAM capacity and speed. I hope this tutorial will answer your question on what is RAM, the RAM capacity and brand as well as different types of RAM.

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