BREAK THE SPEED LIMIT ON YOUR PC'S INFORMATION MOTORWAY
RAM is the less obvious overclocking candidate, as many people still consider it a matter of how much rather than how fast. Well, you can have the largest-capacity stomach in the world, but if your bowels can't clear the contents of it quickly enough you'll still hit nasty overflow problems.
Put less viscerally, memory is the means by which various key elements of your PC talk to one another, so the faster it can shuttle chunks information betwixt processor and hard drive the better. Obviously, the amount you have does matter, as the more you have, the more information can be stored in and called from your hyperfast RAM before a return trip to your far slower hard drive is required.
Perhaps it's just an irritating "I am low on mana" soundbite, perhaps it's a huge chunk of level layout you're impatiently waiting to load. It doesn't matter. If you don't have enough memory to handle the vast amounts of data churned out by a modern game, even the most titanic overclock won't compensate for it. Essentially, it'd be like piling a load of elephants on top of a Robin Reliant then screaming at it to go faster.
And then it gets more complicated. There are two essential speeds for RAM, and even that's simplifying matters somewhat. RAM's clockspeed is relatively easily understood - it's the speed, in megahertz, that the RAM operates at - kind of like a processor. It's tied into the front side bus, discussed in the processor segment of this feature, so in most cases overclocking the CPU also raises the speed of the front side bus, which in turn raises the speed of the RAM. See, everything is connected, maaaaan.
In a perfect world, when you raise the bus speed, as described on the previous page, and both the CPU and RAM speed increase as a result, your PC keeps on running just fine - better, even. In the real world, the RAM often conks out way before the ceiling that the CPU hits. So you need to find a mid-point between the two by lowering the clock speed of your memory so that, when multiplied by the raised bus speed, it's not too much higher than its official speed rating.
On some systems, however, an increase in RAM speed can reap greater rewards than pumping up the processor speed. In this case you'd want to set the memory's clockspeed to the maximum. Many motherboard BIOSes will let you simply set the memory to run faster than its official speed without also changing the bus - 400MHz DDR at 500MHz, for instance. All well and good if it works, and in some cases possibly your only recourse, should your processor hit problems when you raise the bus speed.
So much for the clockspeed. RAM's other key speed is its latency. Very simply put, this is the speed at which various elements of the memory itself communicate with each other internally - that is, before the RAM sends and receives data from other hardware in the PC. It's Mrs Goggins at the sorting office rather than Postman Pat in his van, kind of. That was a remarkably patronising analogy, wasn't it?
Anyway, there are numerous latency types, and aggressive tinkering with each can yield better results, but it's generally simplified as 'CAS' and a number of 5.0 and under. Generally speaking, the lower your CAS latency the better, although effects differ wildly depending on your CPU and motherboard.
AMD chips tend to be happier with a lower CAS latency, while many Intels do best with a faster RAM clock speed. As a rule, the slower the memory's clock speed, the lower the CAS can be - so if you've ramped up the clock speed loads, don't expect to be able to do much with the CAS too.