Continuing the series of posts on building your own PC, we are looking at the things that you need to consider when buying a CPU.  As discussed in the last post we generally should be looking for something that is in the value sweet spot.

Choose something that fits your needs

As with the other components is is important to get something that fits your needs. So you need  to decide up front what you want from your final computer. Is it a media PC, an office type PC,   something as cheap as possible or a high spec gaming rig?  Whichever of these it is, will mean different aspects will be more important to you, but generally the faster the better.

Things to consider when buying a your CPU

1. Motherboard support - Your choice of processor will have some determination on which board you can go for and visa versa. This is because it is important that your choice of CPU is compatable with your choice of board.
2. Vendor - Most people will probably go for for Intel but there are other options such as AMD who are producing some fast processors  and providing some good value at the basic end of the market.  Make sure you check your motherboard support!
3. Multiprocessors - The questions here is not whether to get a multiprocessor, as my recommendation would be to by a least a Core 2 Duo or its AMD equivalent, but whether to go for a Quad Core. Unless you have an application that can really take advantage of the Quad Core I would stick to the Core 2 Duo.
4. Clock speed - In general the faster the better. But be careful as clock speed is only a valid way of comparing processors of the same architecture such as the Core 2 Duo.
5. L2 Cache - A bigger L2 cache memory will generally speed up a processor’s operations. It does this by saving recently accessed data and making it available much quicker to the processor.
6. FSB - On Intel chips a faster FSB (Front Side Bus) will allow faster performance.

The last two above will have a greater or lesser effect depending on what you are actually doing on the computer but may allow a lower clock speed processor to perform better than another with a higher clock speed due to a larger cache and faster FSB.  To finish off with an example the Intel Core 2 Duo E8400 Dual Core has the same clock speed and FSB as the Intel Core 2 Duo E6850 Dual Core we looked at in the last post but has a bigger L2 cache.

What do you look for when buying a CPU?