Choosing The Right RAM For Computer

Sunday, March 17, 2013 1 Comments A+ a-

We’ve looked at the relationship between CPU speed and overall PC speed. Basically, the faster the CPU, the faster the PC will run applications. Think of your CPU like a car engine. The bigger the engine, the more power the car will have.When the PC isn’t working very hard, you might not notice this extra CPU power (you don’t notice that a car has a big engine when you are driving at 30 mph, but you do notice it when the going gets tough).

If CPU power is analogous to the size of an engine in a car, then RAM is comparable to the overall size of a vehicle. In much the same way that you can get more people into a big car, if you have more RAM you can run more programs simultaneously. Engine size is still important if the vehicle is going to drive smoothly under a heavy load.

In this chapter, we are going to be looking at RAM, different RAM types, and how much RAM you should install into your PC.

Understanding RAM

RAM (an acronym for random access memory) is a working memory space that PCs use to load data and programs that are regularly accessed. The data stored in RAM can be accessed in any order (hence the word “random”) as opposed to, say, data stored on magnetic tapes, which has to be read sequentially (this format is uncommon nowadays other than for backups). The “random” in the name is a historical throwback much like the terms “hard” drive and “floppy” drive (early floppy disks were made of soft material and were floppy).

The main reason for loading data into RAM as opposed to accessing data directly off the hard drive is that it’s much faster to access data from RAM than it is from a hard drive.To give you an idea of just how different the access speeds are, data access speeds from a hard drive are measured in milliseconds (thousands of a second); RAM access speeds are measured in nanoseconds (billionth of a second).

There’s another crucial difference between RAM and hard drives.While there’s no doubt that RAM is much faster than hard drives, hard drives have the upper hand when it comes to capacity.While hard drives can now be measured in hundreds of gigabytes, RAM modules are at mostly around 1 GB. Commonly used RAM modules sizes range from 128 MB to 512 MB. RAM comes in the form of memory modules (or chips) mounted on circuit boards. These circuit boards are fitted onto the motherboard via the RAM module slots on the board, known as banks.

It used to be that RAM modules had to be installed in pairs of similar modules, so if you wanted a PC that had 64 MB of RAM you had to install two 32 MB modules. Three drawbacks of this system were that:

You always needed two modules instead of one, which meant that manufacturers had to keep a larger inventory of modules. An upgrade sometimes meant throwing away two modules.There was twice the chance of being affected by a faulty memory module when adding new RAM modules. 

Technology has progressed and now modules can be installed singly, which is both cheaper and less hassle overall. However, be aware that you might get better performance from having RAM in both banks because the motherboard makes use of a technology known as “dual-channel.”

Types of RAM

A number of different types (or styles) of RAM are available. These different types come about from advances in technology as older types are replaced by newer, faster technologies. Here you’ll take a tour of the RAM types supported by current motherboards. This means that if you are using this book to help you upgrade a current system, the RAM you have may not be mentioned here.


Currently, the most popular type of RAM in use is called DDR RAM. DDR stands for “Double Data Rate” and the “double” comes from the fact that it utilizes technology that makes it twice as fast as regular SDRAM (Synchronous Dynamic Random Access Memory) upon which it was based.

DDR does this amazing trick of being able to transfer data at twice the standard operating speed of the RAM by transferring data on every rising edge and falling edge of the clock pulse. This is a huge advantage compared to SDRAM. For example, if you assume a clock speed of 100 MHz, SDRAM will transfer data only on every rising edge of the clock pulse, thus having an effective transfer rate of 100 MHz. DDR, being able to transfer data at the rising and falling edge of the clock pulse, has an effective transfer rate of 200 MHz.

Keeping everything else equal, this doubling of the transfer rate alone represents a huge gain in performance. However, as with most things, more was demanded from RAM.


The “2” in DDR2 refers to the fact that this new technology again represents a doubling of the data transfer rate when compared to DDR. This additional doubling of the speed of the RAM is due to improvements made on the chip rather than additional transfers made per clock cycle.

DDR2 also requires less power than DDR and SDRAM, reducing system power consumption and heat generated (making it handy in laptops).

Deciding How Much RAM to Install

After you know what kind of RAM your system needs (or you decide to use a vendor to supply the right RAM), you come to the question of how much RAM to install.

Modern motherboards can all take in excess of 1 GB of RAM, while the smallest RAM module you can buy these days is 128 MB.Typical motherboard limits are somewhere around 1 to 3 GB. Don’t try to exceed this figure because things will go wrong (at the very least your system won’t recognize any amount over the limit, the worst case scenario being that it won’t boot up at all).

So, your motherboard maximum is one ceiling to bear in mind. However, there’s another memory limit, and that is the one imposed by the operating system you plan to install.


In this tutorial, we’ve looked at RAM and its function in a PC. We’ve also looked at the different types of RAM available (DDR and DDR2) and what these differences mean. We’ve seen how to ensure compatibility between motherboard and RAM modules and how you can get the right amount of RAM for your new system.


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