Choosing a computer - RAM

JPCT 150713 Alan Stainer. Photo by Derek Martin
JPCT 150713 Alan Stainer. Photo by Derek Martin

RAM, or Random Access Memory, is the part of the computer that holds data in temporary storage for the CPU to access.

My goodness that sounded dry, like an old school text book. Let’s try again with an analogy.

If the CPU is the brain of the computer and the hard drive is long term memory, then RAM is short term memory. It’s faster to pull something from RAM than it is from the hard drive, which means it is perfect for the CPU to work with.

This does of course mean that the numbers you see written for different types of RAM are important. The size of the RAM, or rather the capacity, is obviously going to be important. Capacity is measured in gigabytes these days, or GB for short. So a computer with 16GB of RAM can hold twice as much information for the CPU to access as a computer with 8GB. The theory goes that the computer with the larger sized RAM will work faster, because it will need to access the hard drive less often.

This is of course true, although the speed of the RAM is important too. When buying a new computer, or just RAM if you are looking to upgrade or build your own PC, you need to pay special attention to the speed of the RAM. RAM speed is measured in MHz. So RAM listed as 3000MHz is going to be quite a bit quicker than RAM listed as only 1600MHz.

While we are still on the subject, everything about RAM so far also applies to graphics cards, which have their own set of dedicated RAM. I’ll come back to that another time.

As with all things in the technology world, standards change over time. The latest version of RAM that you will see mentioned is DDR4. Predecessors in the DDR standard are (obviously) DDR, DD2 and DDR3. Generally speaking, DDR4 will be faster and have greater capacity than DDR3 and so on.

As well as the speed, capacity and type of the RAM, you will often see RAM listed as being dual or sometimes quad channel.

What the heck is that you may be wondering. It isn’t that hard a concept to grasp, so I shall try to explain. Imagine your RAM is a single body of water, perhaps a lake. If there is a single stream feeding the lake and another one emptying it, that would be a single channel setup. Now imagine you have two smaller lakes that equal the size of the first big lake. Each lake has a stream going in and coming out. That is dual channel. Scale it up again to four lakes and four streams going in and out, and you have quad channel. The greater the number of channels that are being used, the greater the amount of information that can be transferred at any one time.

What this means in practice is that a computer with 4GB of RAM (for example) could be set up in three different ways. The first and potentially the slowest, would be a single stick of 4GB. The second option would be dual channel, which would be 2x2GB. The third and potentially fastest option, would be quad channel with 4x1GB.

Now, can you remember all that?

Alan Stainer