Everything You Need to Know About Desktop Memory
Understandably, entertainment expenses like computer games are usually the first thing cut out of the average budget when tough economic times arrive. When it comes to your gaming rig, in many cases upgrading a component or two can boost your performance at a fraction of the cost of replacing the entire machine. Adding memory is one of the easiest and most common ways to extend the life of your desktop gaming PC, but the growing varieties of RAM can make it a befuddling process for newcomers.
How Much Do You Need?
Sluggish PC performance, particularly in MMOs, is often caused by a shortage of memory rather than a lack of processing power. The amount of RAM in your computer affects how often the (much slower) hard drive must be used to store information, which can make a big difference in how smoothly a game runs. 2GB of RAM is the standard for a gaming rig these days, so if you have less than that in your system, memory is likely the first upgrade you will want to consider.
How do you know how much RAM your computer has? If you are familiar with your system's bios, it will normally tell you not only how much memory you have, but also which DIMM slots are being used, and whether or not it is in dual-channel mode. System information in your Windows Control Panel is another simple way to find out how much memory you have, although it only gives you a total.
The Upper Limit
Generally speaking, more RAM is always better, but it is important to note that we are now reaching the limits of the most popular 32-bit operating systems. The 32-bit version of Windows XP that still resides on the majority of home computers supports only 4GB of physical memory, and that limit includes memory on your video card. Subsequently, any physical memory over 4GB will go unused until you upgrade to a 64-bit version of Windows XP or Vista (and a 64-bit CPU if you don't already have one). On the other hand, 2GB sticks of RAM are very affordable and convenient, so having a portion of your memory going unused is far better than having too little memory.
Those of you that have already gone 64-bit can enjoy quantities of RAM that are only limited by what their motherboard will support. Although a 64-bit OS allows a 64-bit CPU to address millions of Terabytes of RAM in theory (2^64, to be exact), for practical reasons, Microsoft has limited their 64-bit versions of Windows to 128GB of physical memory. Many newer boards support up to 16GB, but most people are still using boards that top out at 8GB.
DDR vs. DDR2 vs. DDR3
Another thing to consider is how many DIMM (Dual Inline Memory Module) slots your motherboard has and what type of slots they are. Older boards might be using 184-pin DDR SDRAM (92 pins per side), while the standard is now 240-pin DDR2 (120 pins per side). In that case, it would be wise to postpone buying more RAM until you're ready to replace your motherboard.
As you might have guessed, the never-ending quest for speed has recently produced DDR3 RAM. Only a handful of Intel-based motherboards currently support DDR3, so it isn't a concern unless you're considering a major upgrade. AMD plans to offer processors with DDR3 support using socket AM3 in early 2009.
Memory Slots and Speeds
Most full-size ATX motherboards have four DIMM slots, although some smaller form factor boards have only two. Typically, when you use modules of the same size and speed in either two or four slots, you gain the benefit of dual-channel mode. While this mode theoretically doubles the RAM's data rate, in practice it rarely makes a big difference in performance. DDR2 comes in several different clock speeds, including DDR2 533, DDR2 667, DDR2 800, and most recently DDR2 1066. When all of your slots are full, the only way to increase the amount of RAM in your system is to replace existing modules with larger ones.
As a result, your current RAM configuration can determine what your best upgrade options are. For example, if you currently have two 512MB modules of DDR2 667 in your system, and two empty slots, buying two more identical modules of DDR2 will give you 2GB of RAM running in dual-channel mode. You can mix up different types of modules, but they won't run in dual-channel mode, and if you use different speeds, they will all run at the speed of the slowest module. Sacrificing dual-channel mode for more memory is usually worth it, especially if you have very little RAM.
The Label Explained
When you go to purchase memory, it will have a lengthy label such as "Crucial 2GB (2 x 1GB) 240-Pin DDR2 SDRAM DDR2 667 (PC2 5300) Dual Channel Kit Desktop Memory." What does all this mean? Crucial is the brand of the memory, 2GB is the total amount of memory in the kit, 2 x 1GB indicates that it comes in two modules of 1GB each, 240-Pin DDR2 SDRAM is the type of RAM, DDR2 667 is the maximum frequency of the RAM in MHz, and PC2 5300 is the memory's bandwidth (a redundant figure since it correlates directly with the frequency). It's a "Dual Channel Kit" because it provides two sticks intended to occupy two slots and operate in dual-channel mode. Another specification that has been getting attention in recent years is memory latency, which is measured in memory bus clock cycles. A set of four digits separated by dashes is used to describe RAM timing, such as 5-5-5-18. The first and most important number is the CAS (Column Address Strobe) latency, sometimes referred to separately as the CL (CAS Latency). The remaining numbers refer to the tRCD (Row address to Column address Delay), the tRP (Row Precharge time) and the tRAS (which is the active to precharge delay). While you should note that smaller numbers are better, they're not likely to have a dramatic impact on your system's overall performance.
Once you've settled on a configuration, adding RAM to your system is a simple task. After opening up your case, you'll find the DIMM slots on the motherboard, usually somewhere near the processor.
RAM slots have small tabs at either end that close when you push the module down, locking it into place. Open the tabs before you put the module in. If there's a module in the slot, opening the tabs will pop it out. You'll notice that there's a notch near the middle of the module that prevents you from inserting it the wrong way. That notch also makes it impossible to put DDR2 in a DDR DIMM slot, and vise versa.
What to Buy
In recent years, I've noticed RAM being sold with added features like heat spreaders and LEDs. These things can be fun if you want your components to look neat, but I wouldn't pay a lot extra for them. Remember, gadgets like these can be purchased separately and placed on any RAM module. Standard offerings from respected brands such as Crucial, Corsair, Kensington and OCZ, which currently sell for around $15-$20 per GB, will serve most purposes just as well.