What am I looking for in RAM?

Question

This is the one area of computer building that still has me in the dark, and I think a lot of people are with me...

There are many different types of RAM, with each company having high and low end sticks. What is the difference between the high and low end?

Also, what do the numbers in the latency mean? What is the speed rating (I know 1600 MHz is about normal) and how much is too much? What's the difference between dual channel and single channel? Can you overclock/overvolt? Is there even a point to do so if this was possible?

As you can see, I'm thoroughly confused here. I tried doing some research, but I can't find this information anywhere on the internet. I'm not actually buying RAM, I'm just trying to get a better picture as to how all this works so I can be more educated on the hardware in computers.

Thanks for all the help guys. A wiki may even be better here, I'm not sure.

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Answer 1

Each stick may have the same speed, but their specifications differ. It's those specifications that make up for a difference in price. To get a different stick you'll need a different way to produce it; as to increase the amount of memory, get rid of the latency and more. It's the difference in the required resources that makes up for the different price, as well as funding the research behind it and all that.

We already have two other questions that answer some of the confusion:

• What do the memory timings and RAM mean? (TM gives a summary, user2751 goes into detail)

• Should I be worrying about Single Channel and Double Channel for my RAM? (under MB image)

As for speed rating, that's somewhat subjective so I think the best bet is to look at some current systems and what they have. This will quickly show you what the current speeds are at and what would be considered too much or not enough.

I haven't seen memory overclocking other than changing some latency related settings in the BIOS, which I've never found necessary to do so. Memory overvolting might be possible to provide more stability as you change the latency settings, but unless you do very memory intensive jobs it is most likely not worth it.

Answer 2

You will also have to look to the RAS-CAS latencies. These will be different between those sticks. It's something you can consider depending on what you are building. The lower, the better and the more expensive.

RAM is organized into rows and columns, and is accessed by electrical signals called strobes, which are sent along rows to the columns; when data is needed, the CPU activates the RAS (Row Access Strobe) line to specify the row where data is to be found (high bits), then, after a short time, the CAS, or Column Access Strobe, to specify the column (low bits). After that, the data goes to the output line and to its destination on the next clock tick. In other words, the Column Address Strobe dictates how many clocks the memory waits before sending data on. All registers should be full, or errors will result, which means a longer wait to make sure, and slower operation. The shorter the cycle length, the faster the machine runs, at the expense of stability and data.

RAS CAS