How to Buy the Best Computer Memory

This article will focus on helping you understand and choose the best computer memory for your PC. Random access memory or RAM for short is memory located in slots on your motherboard. The computer temporarily stores data and programs in RAM. The CPU transfers applications and data from long-term storage devices (hard and optical drives), then runs the programs and accesses data from RAM as needed.

Every byte of information used by the computer flows through RAM on its way to input/output devices, the CPU, or a hard/optical drive for long term storage. Access time to data stored in RAM is immediate, since it is an electronic device unlike the electro-mechanical hard drives and optical drives which are slow in comparison.

RAM and the Paging/Swap File

What happens when a program or data file exceeds the amount of RAM installed in your computer? PCs use dedicated space on the hard drive called a paging or swap file to store overflow data from RAM. This is an example of virtual memory and is temporary storage for data that exceeds your computer's memory capacity. I know what you're thinking. Why should I know or care about this? There are consequences when the computer has to make use of a swap file. Especially when it does so on a continuing basis. This is indicative of too little memory installed. Another indicator is the hard drive activity light flashing every few seconds even when the computer is at idle.

Not having enough memory is also has a huge negative impact on system performance. In other words, it slows your computer way down and here's why. Hard drives handle data an order of magnitude slower than even the slowest RAM. This means that having more of the best computer memory is a definite plus for PC performance. More memory allows you to run more programs simultaneously, and allows you to store more data for faster access by the CPU to speed things up. How much memory your computer has directly affects the speed of your programs and how well they perform. Adding more of the best computer memory to your PC is the least expensive and most reliable way to boost your computer's performance.

Types of Memory

There are four types of memory that you may encounter. DDR RAM is the most common and will probably be what you choose for your motherboard. The four types of memory follow.

• RDRAM(Rambus Dynamic Random Access Memory)- Depending on your motherboard selection you might run into this type of memory. It was originally developed for use with the Pentium 4 processors and has a high bandwidth. XDR DRAM, RDRAM's successor is used by IBM's cell processor and the Sony Playstation 3. Comes in the form of 16 bit 184 pin RIMMs (rambus in line memory modules).
• SDRAM(synchronous Dynamic Random Access Memory)-This type of memory actually synchronizes with the front side bus and processor. This increases its speed and efficiency at processing data. Comes in the form of 168 pin DIMMs (dual in line memory modules)
• DDR SDRAM-Currently the most common type of memory DDR(Double Data Rate) has doubled the speed of SDRAM by sending and receiving on the rising and falling of each clock cycle respectively. This or the newer DDR2 is the memory of choice for the best computer memory. Fast and reliable. Packaged usually as a 184 pin DIMM.
• DDR2 SDRAM- Second generation DDR memory that provides greater bandwidth along with other new features. These include lower operating voltage, and On-Chip termination (OCT). Growing in popularity and will probably replace DDR in the near future.

Considerations When Choosing the Best Computer Memory

The first consideration when choosing the best computer memory for your PC is what type, speed, and how much you will need. Make sure you know the type, speed and capacity your motherboard manufacturer recommends. The motherboard manufacturer is the definitive authority for this information. Of course if you're building a system you need to decide on a motherboard first.

Speed

The next problem is figuring out the naming and numbering scheme the manufacturers have concocted to label memory. There is a method to the madness. Here's a question.. How do you know if you have 133 MHZ, DDR266, or PC2100 DDR memory? The answer is, it's all the same memory! Because DDR266 runs at a clock speed of 133 MHZ, but makes two writes or reads for every clock cycle, the real speed of the memory is 266 MHZ.

DDR memory is also labeled by its throughput or bandwidth. For example DDR266 has a throughput of 2.1 GB/s, so DDR266 is also called PC2100. It kind of makes sense. Keep in mind that the bandwidths referred to are with memory in the single channel mode. When memory is used in the dual-channel mode the bandwidth is doubled. For example, the bandwidth for DDR333 provides 5.4 GB/s in dual channel mode versus 2.7 GB/s in single channel mode. More later on dual channel.

CAS Latency/Timing for the Best Computer Memory

CAS is an abbreviation for column address strobe, which is a signal sent to the DDR memory indicating a column address. SDRAM stores data in matrixes with columns and rows. Data is retrieved from these matrixes by using signals for their co-ordinates. Similar to locating a point on a map using latitude and longitude. CAS latency is the amount of time between the request for data and the delivery of that data. As you might guess, the smaller the number the better. The upshot is that you're looking for a small CAS latency to buy the best computer memory.

ECC Registered/Unbuffered

ECC stands for error checking and correction. To make a long story short, if you're not building a server or a workstation, you don't need ecc/registered memory.

Unbuffered memory refers to the memory controller being able to address each memory chip on all modules at the same time, whereas in ecc/registered memory the memory contoller sees all the memory as a single register. Most consumer motherboards use unbuffered memory so it's not something you should be concerned with.

Dual Channel Memory for the Best Computer Memory

This is a motherboard dependent feature that effectively doubles the bandwidth of PC memory. Two indentical memory modules are used because they offer less compatability problems and deliver better performance.

Which is Best

The most important point when choosing memory is compatability. Make sure your system supports it before buying. If you're building a system, check your motherboard specifications either online or in the motherboard user's manual. Keep in mind that 512 MB is the minimum amount of memory needed in a computer.

If you are a gaming enthusiast double that for a total of 1 GB of memory.

When all is said and done remember that more is better and select memory from a well known manufacturer such as Crucial or Kingston.

Where to Buy Memory

Make sure you know what type and speed of memory your motherboard manufacturer recommends. Then to insure the best computer memory buy quality brand name memory such as Corsair or Kingston.

Find the best computer memory deals online here.