How much is enough? We show you how to get the most from your computer's memory.
With the price of memory dropping faster than Julia Gillard's poll results, many people have started to overlook the importance of these sticks of short term storage salvation. Whether you're trying to run Windows 7, editing HD videos or playing a game chock full of high resolution textures, your system's memory can make or break your day. Too little and your poor little hard drive will be thrashed to within an inch of its life. Too much and you've wasted your cash on silicon that simply sits there, cold and unused. We're here to show you how much memory you'll need, how to install it, and how to tweak it via your BIOS. Sit back and prepare to become a Memory Master!
Memory Type
The first tip is an easy one - make sure you buy the right type of memory, either DDR2 for legacy systems, or DDR3 for recent builds. The two types aren't compatible, make sure you buy the right kit, it will save you a trip back to the store. When it comes to speeds, it's best to buy the highest speed that your motherboard supports, unless you're overclocking.
How much is too much?
The amount of memory you require depends very much on what you're using your PC for, as well as the type of motherboard you're using. Here's a good yardstick for figuring out how much you'll need.
2GB If you're running Windows XP, firstly shame on you. Secondly, you can make do with a mere 2GB of memory as this operating system has a baby-sized footprint. You can probably scrape by with 2GB if you're building a Windows 7-powered media box that only has to share files and play videos.
4GB This is the perfect amount for the memory hungry beast that is Windows 7. Any less and you'll find your PC taking a trip to chug town every time you open up multiple applications at once. It's also plenty for all but the most demanding of PC games. Most of today's motherboards have a dual channel memory design, so if you're going for 4GB total, ensure you buy two 2GB sticks to maximise performance.
6GB This unique amount of memory is recommended for those running a motherboard chipset that has triple channel memory support, which currently is limited to Intel owners running the Core i7-900 and Xeon series. This technology is targeted more at the server market than desktops.
8GB If you're a budding amateur Spielberg, Photoshop wizard or hardcore gamer, 8GB provides plenty of memory for your needs. The same dual channel rule for 4GB applies here, so buy two 4GB sticks to get the best performance out of today's dual channel motherboards.
8GB+ Only those who spend a serious amount of their day editing large HD video files, massive image files, serving data to other PCs or very specialised memory hungry programs need to worry about such large amounts of memory. It's way too much for us mere mortals.
Memory Voltage
Much of today's affordable DDR3 memory is certified to run at 1.65V, which confuses many people when their motherboard says to only supply 1.5V memory. Fear not, as it's perfectly safe to run your memory at the higher voltage of 1.65V. Newer DDR3 memory sticks are hitting the market with a voltage rating of 1.5V, but they're still in the minority.
Installing Memory
As we mentioned before, most of today's Intel and AMD boards use a dual channel memory design. As a result the motherboard chipset delivers better memory performance when you're using two or four of the memory slots, and slower performance when using just one or three memory slots. Most motherboards today have four memory slots, and they're grouped in pairs, which can usually be identified by matching slot colours. Always fill the matching coloured slots first, otherwise the dual channel feature will not work. Having said that, some motherboard manufacturers like to confuse matters by putting the paired memory slots next to each other, so consult your mobo manual to check which slots should be filled to enable dual channel support.
When installing memory, don't wear the woolly jumper your Gran knitted for you as you're doing it. RAM is susceptible to electrical shock damage, so you want to minimise any static electricity build up before touching the RAM. The expensive way to do this is to buy an ESD wristband, but our ghetto method has worked just as well for us over the last decade; with your PSU plugged into the wall, simply tap the exterior of the PSU case. This will get rid of the small amounts of static our body builds up.
RAS, CAS, WTF?
There are literally dozens of different memory timings and settings that you can tweak, but you'll get the most performance increase by understanding just a handful. Once you've got your memory installed and running stably, try decreasing the following values one at a time to increase your overall memory performance.
CAS (tCL) Timing: 4-4-4-8: In this example the first 4 refers to your memory's Column Address Strobe value. Lowering this decreases the time between sending a read command and the time it's acted upon.
tRCD Timing: 4-4-4-8:This is the RAS to CAS delay, and in our example is the second 4. Lowering this decreases the time between issuing an active command and the read/write commands.
tRP Timing: 4-4-4-8:In this example the third 4 is the Row Precharge Time, which is the minimum time between active commands and the read/writes of the next bank in the memory module.
tRAS Timing: 4-4-4-8:The final important RAM timing refers to the Min RAS Active time, and is the number 8 in our example. It refers to the amount of time between a row being activated by precharge and deactivated.
You can possibly squeeze slightly lower values out of your memory than what it's rated at, and a very small increase in the memory voltage might help in this regard.
Extreme Memory Profile
If you see the Intel XMP logo on your RAM kit, it's compatible with this supercharged method of memory timing. By enabling the XMP timings in your BIOS, this automatically overclocks the system memory to slightly higher speeds. Don't enable the XMP option unless your memory specifically states it's compatible with this feature, otherwise you'll be left with a very unstable PC.
Memory Overclocking
Overclocking memory can take a lot longer than CPU or GPU overclocking, simply because there are so many variables to tinker with. All of the timings mentioned above can have an impact, as well as many more buried in the BIOS, but in the opposite way you might expect. Generally speaking, you need to increase these timings to increase the overall frequency of the memory. Once you've eased off on the default timings of your memory, it's time to look for the memory ratio or memory multiplier. Unfortunately the name of this is different for every board on the planet, but look through your BIOS and find something that sounds like it. Adjusting this value should show you the resulting memory speed - try bumping it up a notch so that your RAM is running at a higher frequency, before running memtest to check for stability.
Memory is one of the three prongs of the holy trinity of PC performance, alongside the CPU and GPU. Having the right amount of memory is crucial to keep performance acceptable, and making sure you've installed it correctly will make sure it's giving you all that it has got. If you want to get your hands really dirty, feel free to tweak the timings, but don't expect massive leaps in real world performance.
