Wednesday, February 16, 2011

RAM : What is it?

Recently, someone asked me about RAM :
  • What it is and why it is important?
  • What are the types?
  • How to upgrade memory?
So, i thought to dedicate this post to RAM.


WHAT IS RAM?
Random Access Memory is the most common computer memory which can be used by programs to perform necessary tasks while the computer is on. It is called "Random" because it allows data to be accessed randomly. RAM is used by the system to store data for processing by the processor. When the computer is turned off, all the data in the RAM memory is lost.

There are three types of RAM available today:
  • DDR SDRAM: Double Data Rate Synchronous Dynamic Random Access Memory is a class of memory integrated circuits. Compared to the preceding single data rate SDRAM, the DDR SDRAM interface makes higher transfer rates possible by more strict control of the timing of the electrical data and clock signals. With a bus frequency of 100 MHz, DDR SDRAM gives a maximum transfer rate of 1600 MB/s.
  • DDR2 SDRAM: DDR2 SDRAM supersedes the original DDR SDRAM specification and the two are not compatible. In addition to double pumping the data bus as in DDR SDRAM, DDR2 allows higher bus speed and requires lower power by running the internal clock at one quarter the speed of the data bus. The two factors combine to require a total of 4 data transfers per internal clock cycle. With data being transferred 64 bits at a time, DDR2 SDRAM gives a transfer rate of (memory   clock rate) × 2 (for bus clock multiplier) × 2 (for dual rate) × 64 (number of bits transferred) / 8 (number of bits/byte). Thus with a memory clock frequency of 100 MHz, DDR2 SDRAM gives a maximum transfer rate of 3200 MB/s.
  • DDR3 SDRAM: DDR3 SDRAM is a Random Access Memory interface technology used for high bandwidth storage of the working data of a computer. DDR3 is part of the SDRAM family of technologies and is one of the many DRAM(dynamic random access memory) implementations. DDR3 SDRAM is an improvement over its predecessor, DDR2 SDRAM, and the two are not compatible. The primary benefit of DDR3 is the ability to transfer at twice the data rate of DDR2 (I/O at 8× the data rate of the memory cells it contains), thus enabling higher bus rates and higher peak rates than earlier memory technologies. In addition, the DDR3 standard allows for chip capacities of 512 megabits to 8 gigabits, effectively enabling a maximum memory module size of 16 gigabytes. With data being transferred 64 bits at a time per memory module, DDR3 SDRAM gives a transfer rate of (memory clock rate) × 4 (for bus clock multiplier) × 2 (for data rate) × 64 (number of bits transferred) / 8 (number of bits/byte). Thus with a memory clock frequency of 100 MHz, DDR3 SDRAM gives a maximum transfer rate of 6400 MB/s.

Some general terms regarding RAM:

XMP: Extreme Memory Profile – Some RAMs supports this feature. This automatically sets the RAM timings in BIOS so you don’t have to.
ECC: Error Correcting Code - ECC can actually correct errors in RAM (if any) without interrupting the other operations of your system.

CAS Latency: Column Address Strobe (CAS) latency, or CL, is the delay time between the moment a memory controller tells the memory module to access a particular memory column on a RAM memory module, and the moment the data from given array location is available on the module's output pins. In general, the lower the CAS latency, the better. CAS Latency is available in 2,3,5,7,9,11.

Dual Channel: Dual-channel architecture describes a technology that theoretically doubles data throughput from the memory to the memory controller. Dual-channel-enabled memory controllers utilize two 64-bit data channels, resulting in a 128-bit data path. Dual-channel architecture requires a dual-channel-capable motherboard and two or more DDR, DDR2, or DDR3 memory modules.

Triple Channel: DDR3 triple-channel architecture is used in the Intel Core i7 family of processors (9xx), which are used on the Socket LGA1366 platform (X58).
     AMD Socket AM3 processors do not use the DDR3 triple-channel architecture, but use DDR3 dual-channel memory kits instead. The same applies to the Intel Core i5 and Core i7 (8xx) processor family, which are used on the Socket LGA1156 platform (P55).
     When operating in triple-channel mode, memory latency is reduced due to interleaving, meaning that each module is accessed sequentially. Data is spread amongst the modules in an alternating pattern.
     The architecture can only be used when all three, or a multiple of three, memory modules are identical in capacity and speed, and are placed in three-channel slots. When two memory modules are installed, the architecture will operate in dual-channel mode.


How to Choose and Upgrade RAM




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Wednesday, February 02, 2011

Join Multiple PDF files with ease

A nice neat PDF trick.....

Many people uses Adobe PDF (Portable Document Format) a lot. Why? Because they are easy to create, they are portable and  can be secured with a password. Infact all the online ebooks, manuals, bills etc. are in a pdf format.

Sometimes, a situation occurs when you have a lot of pdf files and want to have them all in a single file. The solution is : PDFJoin!
      PDFJoin! is a powerfull PDF files merger and you don't even have to install any sort of program to join the files.
All you have to do is go to http://www.pdfjoin.com/ then select your PDF files and click Join!

That's it. Your merged PDF file can then be downloaded.


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