FSB (Front Side Bus):

In simple terms, FSB is the data transfer speed between the CPU, Northbridge and memory modules. It’s measured in MHz and raising it virtually affects everything. You raise the processor MHz speed and bandwidth, the motherboard bus and the memory frequency and bandwidth all at the same time.

CPU clock multiplier:

The CPU clock multiplier is nothing more than a processor setting which determines the MHz speed. If you multiply the multiplier with the FSB MHz, you have the processor resulting clock speed. For example, a 166FSB setting and a multiplier of 11x will result to (approximately) 1833MHz speed. That’s an AMD Barton 2500+ stock setting.

Voltage regulators:

Voltage regulators are present on the motherboard (usually) and by tweaking them you can change the voltage supplied to the components of your system. These tweaks can be done through the BIOS on most boards that where built the last 3-4 years, else they can be done by jumpers on the motherboard or not at all. The most usual one that you can find on a motherboard (but not always) are:

Vcore:

This affects the voltage supplied to your CPU. It is necessary for overclocking a CPU but only when the cooling is proper and at a decent level. If you raise it too high the CPU will need to be ‘upgraded’ really soon.

Vdimm:

This setting affects the voltage supplied to the memory modules. It is necessary for overclocking the memory and achieving stability with lower timings. Memory modules won’t die instantly from overvolting but it will surely shorten their lifespan enough.

VAGP:

This setting affects the voltage that will reach the AGP port. When video cards where taking all of their power from the AGP slot, that setting allowed them to overclock better. However now that most cards take their power directly from the power supply unit, it’s nearly useless. It helps only to stabilize the system at VERY high FSB speeds when it’s risen a little, which only extreme overclockers care about. If this setting is misused it can kill a precious video card fast.

VDD:

This setting affects the voltage that will be sent to the northbridge chip of the motherboard. It helps the motherboard to achieve higher FSB speeds stable. It only really appeared on the latest N-Force 2 chipset motherboards and still on the few select out of them that were meant to satisfy the overclockers market. By raising it, it can kill the motherboard at high amounts, however it will usually just make the system unstable instead of helping it. Better cooling on the northbridge is required 95% of the time for tweaking that setting.

Memory Timings:

In very simple words, memory timings manipulate the number of clocks (time) that the memory modules will require between changing and issuing commands. Lower timings give better performance since the memory will require less time for its commands. Many memory modules will not work at all at very low timings. However some memory modules cannot work with very high timings either, due to their design. Memory timings are named differently in the BIOS of each motherboard, but usually are referred as CAS latency, Active to Precharge delay, RAS to CAS delay and RAS precharge delay. For every setting lower is better, to the minimum of 2 – 4 – 2 – 2 settings for those. The RAS to CAS delay, even if it isn’t very important, is the hardest to satisfy. Many modules won’t even power up with that set lower than 3.

EMI and heat:

When overclocking, EMI (Electromigration) is probably one of your worst enemies. It is caused in any component when a part of it receives too much voltage and is a lot accelerated by heat. CPUs suffer most from it. That is what will kill a CPU if it exceeds the top temperature limit even if it will be working at the stock speed. This limit is over 70c for most CPUs on the market so I do not think it will be easily achieved if the CPU is not overclocked. However, when overclocking certain parts of the CPU core will get too warm. When you apply more voltage, you just multiply their heat. These parts are usually pieces of the core that need to use too much power to get their job done or parts that aren’t in direct contact with the surface/die so they can’t be directly cooled. Don’t be fooled from the core size and thickness, it may be nearly negligible but it isn’t nil. And micro-technology pieces are way smaller than you can imagine. It is very important to keep components under a certain temperature limit when they are overclocked, which limit depends on the component and never use too much voltage even if you are using extreme measures for cooling, EMI will still occur. Low temperatures will merely slow it down, not stop it completely.