- How much do I need?
- What are the different types?
- DDR SDRAM
- DDR2 SDRAM
- ECC memory
- Mixing memory
- Memory price and brands
- Performance factors
- Dual memory channel
- Buffered and unbuffered memory
If you're buying a new PC, building your own or planning to upgrade an old one, getting the memory right is crucial. In everyday operations, memory is quite possibly the most important performance factor in your PC. Not having enough memory will slow your PC down far more than getting a processor that is a few hundred megahertz (MHz) off the pace.
Computer memory is commonly referred to as RAM - for Random Access Memory. You can think of RAM as your processor's "working space", a place where data and instructions can be stored temporarily for quick delivery to the processor (CPU). Unlike hard disk space, RAM is usually volatile storage, meaning that the RAM is emptied when the computer is powered off and any information held in RAM is lost. Your computer will not run without RAM, and it will not run well if you don't have enough RAM.
There's no quicker or cheaper way to give your PC a shot in the arm than to install more RAM.
How much do I need?
As a rule, the more RAM the better. Run a typical modern operating system (OS) such as Windows XP, plus a few applications, or a single game, and there's a very good chance you will exceed your standard system memory.
What happens then? Your OS calls on virtual memory. This enables you to keep working but, from a performance perspective, virtual memory is very bad news.
When your PC runs out of physical memory, the operating system starts to use the hard disk to store temporary data. The hard disk acts like a memory extender -- this is called virtual memory. The problem is that the hard disk has a lot slower access speed than real RAM, so when the processor wants to recall something from virtual memory, it takes a relatively long time. If you have ever switched between applications in Windows and found that it takes a few seconds and your hard disk churns violently before the application changes over, that's because it's accessing virtual memory. In fact, if you ever find you're waiting for your computer to complete an operation, there's a pretty good chance that the delay is because the computer is using virtual memory.
To minimise the chance of accessing virtual memory, you need to have a system with enough RAM to support the things you want your computer to do. There is no upper value limit on memory (the more the better) although, with a typical Windows XP system, you will start to see diminishing returns after about 1.5 gigabytes (GB). Here's a quick guide to the memory requirements of applications:
- Basic office functions: bare minimum 256MB+; optimum 1GB.
- Presentations with graphical elements: bare minimum 512MB; optimum 1GB.
- Basic multimedia applications (eg, photo editing, multimedia presentations, sound editing, games): bare minimum 512MB; optimum 1GB+.
- Advanced multimedia (eg, animation, real time video editing, solid modelling): bare minimum 1GB; optimum 2GB.
- High-volume database server: bare minimum 2GB; optimum 4GB+
As we've said, a RAM upgrade is more likely to improve the overall performance of a system than a new processor. Memory is not expensive, and you'll really notice when you don't have enough of it.
The maximum amount of RAM you can have in your PC is largely determined by the number of RAM slots on your PC's motherboard. Single modules can be purchased with up to 1GB of RAM. Typical PC motherboards have 2-4 memory slots. Sometimes, you may have to swap out smaller modules if you want to upgrade with larger ones, simply because you no longer have any slots free.
You can freely mix and match modules of different sizes (having, for instance a 256MB module in one slot and 1GB in another). It is less advisable though, to mix and match memory brands and types.