This is the "driver seat" of a computer. There are many different kinds of CPU socket out there. Some are "slots" and some are sockets. Most of the "medieval" motherboards came with sockets such as those 80286, 80386 and 80486 PCs. Those with slots are mainly found in some early Pentium II, III class computers. And all modern CPUs can only be fitted in sockets. For a typical computer user, I bet seldom people would bother with such difference. But for those PC enthusiasts, it is very important for them to distinguish which platform is suitable for which CPU before they pay their cash for these high-tech toys.

CPU is the soul of a computer. Its frequency (both internal and external) and internal cache determine how fast your computer will be. If you are a PC lover, you must be aware of a term known as "overclocking". It is a trick for achieving the highest possible CPU speed by increasing either the front side bus frequency or the clock multiple from the Bios menu (some by setting jumpers). The trade-off is you might shorten the life span of your CPU or suffer from the system instability because of over heat. Unfortunately, most brand-name computers (e.g. HP, Dell, Compaq and so on) do not allow you do so. The reason is crystal clear. If everyone "upgrades" his computer this way, who would pay more for the high-end models. Besides, a severe damage may be posed to your computer if you do not have a "comprehensive training" or enough experience for that. For some very experienced users, they can even tell the overclocking ability of some CPUs by just judging the model number of that CPU.

Some useful hints for system builders:
1. Never buy the CPU with "high micron value" (e.g. 0.18) , buy those marked with 0.13 micron only. Reasons: Less heat and higher chance of successful overclocking. Example: P4 2.0 and P4 2.0A look alike but they are not, "A" here implies 0.13 micron.
2. Spread a very thin layer of heating glue over the CPU surface, if too much, heat will be trapped and you get the reverse effect.
3. Buy a whole copper-made CPU cooler with at least 7,000 rpm fan speed if there is no such term as "speed limit" in your dictionary. My P4 2.0 A is now running at 2600 Mhz without any problems, this is not a limit if I can get a more powerful supply from Enermax.
4. If you believe your CPU can go further, but you tried everything already, buy a new ram with higher frequency is your final resort! (but check your chipset model first)