Section 4 - How to Overclock
Technique 1 - Jack the Multiplier
This is the most ideal method as it does not affect anything other than the CPU and so if you mess up, the only thing that gets potentially messed up is the CPU. Furthermore, increaseing the multiplier increases the final speed by the largest steps (increasing the multiplier by 1.0 will increase the net speed by an amount equal to the core speed). Depending on your motherboard, you may only be able to change your multiplier by 1.0. Some motherboards allows changes by 0.5 to give more flexibility/precision.
Now AMD and Intel both realize that people are doing this stuff and thus they are not getting the sales that they want (of the more expensive chips). Intel has responded by upward locking all the multipliers of their CPUs. You can still bring your multipliers down though (we'll see why in a bit). AMD however has approached the issue (as they've always been more partial to OCing) by making two separate product lines, a mainstream line which is upward locked like Intel's and an enthusiast line which is completely unlocked. Also, some Intel processor models (as mentioned above), together with specific hardware, partially unlocked multipliers become an option.
Technique 2 - Raising the Core Clock
This is the probably the most common method for OCing since AMD and Intel have implemented locks on their processors. The good thing about this approach is that you have a lot more control over your OCs i.e., for each MHz you OC the FSB/HTT, you only OC by the amount that is your multiplier which becomes useful as you try and get a feel for your maximum clock. The down side is that you also increase the operation speed of the memory and if you dont have AGP/PCI locks, the speed of the AGP/PCI bus. Not all memory and/or cards can handle the increase in speed so thats why people run into problems.
What do you mean, raising the core clock raises my memory speed? How does this affect me?
You may have seen memory marketed as PC3500 or PC4000 or such -- the slots are designed to operate at PC3200 so how do you think the RAM is marked so high? To get those speeds, you have to increase the ratio of the FSB/HTT because memory speed.
What is all this PCxxxx stuff anyways? What's the speed?
PC1600 = 100Mhz, DDR200
PC2100 = 133Mhz, DDR266
PC2700 = 166Mhz, DDR333
PC3200 = 200Mhz, DDR400
PC3500 = 217Mhz, DDR433
PC3700 = 233Mhz, DDR466
PC4000 = 250Mhz, DDR500
PC4400 = 275MHz, DDR550
The "PC number" comes from the fact that per pair of clock cycles, 16 bytes of data are being transferred (so for PC4400, 16 bytes * 275 = 4400Mbytes/sec)
Technique 3 - A Bit of Both
While it's possible to OC a system purely by increasing the multiplier or by increasing the core clock, another route is a combination of
changing (not necesarily increasing) both the core clock and multiplier
Why would I ever want to drop my multiplier?
Although the multiplier allows for the greatest single-step increases in net clock speed, sometimes the increases are too much for the hardware to handle and more precision is required. Suppose for instance we have a FX55 system (configured 1:1) that has a maximum clock of 3.00GHz (i.e., it will not OC any higher)
- CPU = 200x13.0 = 2600MHz, RAM = 200MHz (Original)
- CPU = 200x15.0 = 3000MHz, RAM = 200MHz (OC via multiplier increase)
- CPU = 230x13.0 = 2990MHz, RAM = 230MHz (OC via core clock)
- CPU = 250x12.0 = 3000MHz, RAM = 250MHz (OC via multiplier decrease & core increase)
As shown above (assuming the RAM can handle the OC), the last configuration nets the greatest performance from both the processor and the RAM.
Ok How do I *Actually* Go About OCing? Gimme the steps please!
Since there are hundreds of board models out there each with its own appraoch to setting clocks and menus and such, there isnt really a be-all-end-all approach to providing a step-by-step method. Generically speaking however the idea is "go into your BIOS, make sure all the controls (clock speeds, voltages etc) are set to manual and then actually go about setting them to the desired speeds". You'll have to have a look at your manual to see how to actually go about doing this.
I have a Dell/HP/Compaq/Packard Bell/IBM/Toshiba etc ... how do I OC?
For the most part you are SOL and as long as you realize this, read on. In some cases (don't count on it though), you can make use of software hacks to overclock your computer. One of the more popular attempts is a via a program called
ClockGen. Having a quick glance at the list of supported boards, it's evident that even ClockGen is not directed at owners of OEM systems but you might get lucky. This is the price to pay for buying an OEM system (i.e., they dont want you to OC: they'd rather have you buy a new system from them)
I dont have an OEM system but I dont have any of the controls you're talking about!!
Well there are two generic cases of this happening: (1) you have an older or el-cheapo motherboard where all the clock options are set via jumpers on the motherboard so you'll defiitely have to dig out your manual to see where those jumpers are and how to configure them or (2) your motherboard has a crappy chipset/BIOS which is not OC friendly. This happens a lot with SiS and (to a much lesser degree) Via chipsets. Generally speaking, you can try
ClockGen but don't count on it ... those chipsets are generally marketed towards a consumer base both not interested in OCing nor has the [supporting] hardware to do so
Is there a Golden Rule?
Absolutely! And it is "
overclock in reasonable increments" -- overclocking 300MHz at a time is both foolish and stupid as 300MHz is too much of a jump to allow you to be able to discern where your actual OC ceiling really is and pushes the system too hard, too fast. A good ballpark number to keep in mind is 5-10MHz at a time on the core clock at a time and checking for stability each time.