My first guide, but I think it's quite good..? I did pretty much exactly what I've said to do, and achieved a stable 3ghz overclock on an E6600 / 800Mhz RAM / Gigabyte DS4
First you want to get rid of any settings that change the CPU voltage or clock speeds automatically when the CPU's idle or under load. You should also make sure that you have set the ram up properly in BIOS (800mhz, correct latencies, voltages, etc).
Now, onto the guide:
The FSB on Core 2 Duo's is advertised at 4 times its real value
So a 1066Mhz FSB is, in reality, 266Mhz.
Each processor is set its default FSB in the factory. It's also set a multiplier.
The multiplier on an E6300 processor is x7, the E6600 has x9 though.
The multiplier, times the FSB, gives you the processors clock speed.
E6600: 266Mhz FSB, x9 multiplier. 266 x 9 = 2400 (near enough), so 2.4ghz.
The memory speed also relates to the FSB.
Some motherboards let you just say "run the memory at 800Mhz, always" - e.g. the ASUS P5B Deluxe.
Other motherbaords let you say "run the memory at 2 times the FSB, always" and give you options to change it to 2.5 times the FSB, or 3x the FSB.
DDR and DDR2 memory is advertised at 2 times its real speed. So in reality 800Mhz RAM runs at 400Mhz. The ASUS and Gigabyte motherboards, however, show the double speed - so when it says your RAM is running at 800Mhz, it's running at 400Mhz.
People talk about running a RAM Divider. Whats that, I hear you ask? Well, remember 800Mhz ram is really 400Mhz. So 533Mhz DDR ram is really 266Mhz.
Say you have your E6600 processor, by default it will run at 266Mhz FSB. And lets say you've bought your ram, and it's rated speed is 533Mhz (which is really 266Mhz). So the FSB and RAM are running at the same speed - both 266Mhz. That's a 1:1 setup.
Now, if your processor was still at 266Mhz but you put your ram up to 800Mhz (400Mhz), that's a different divider - the ram is running faster than the FSB. Let me work this out... uhh.. your FSB would be 266, and your rams real speed would be 400. So 266:400 is the same as erm... 8:12... which is 4:6 so 2:3. You'd be running a 2:3 FSB:RAM ratio.
Confusing eh. You dont really need to know your ratio (aka divider). Bet you feel like you wasted time now. But people talk about it, so now you know.
Ok whatever, so how do you overclock? Yes, the above was ALL relevant. It's a precursor to getting your boootiful core2duo running nice and fast.
So remember, your CPU has an FSB and a MULTIPLIER. The E6600 FSB is 266. The multiplier is x9. We'll leave the multiplier alone (you can make it less, but not more); we'll increase the FSB.
Imagine your FSB was 334Mhz... 334 x 9 is about 3,000 - so 3 Ghz
We can't just stick your FSB on 334, though.
Get into the bios, and find your FSB settings. Move the FSB up from its default 266 to something like 277.
Remember the two different motherboards - one type says "run the ram at X speed and leave it", the other type says "run the ram at 2 times the FSB", and you can change it to 2.5 times the FSB, 3 times the FSB, 1.5 times the FSB... etc. If you had the first type of option in your BIOS, then your RAM will still be set to run at 800Mhz or whatever you've set it at regardless of what you have your FSB set to (which makes things easier later on). But if you had the second type, now, instead of running at 266Mhz times 2, it'll be 277Mhz times 2 - so 554Mhz. If you bought 800Mhz RAM, that's not good enough, huh! You want 800Mhz. So you could change the RAM multiplier option* [see footnote 1] in the RAM settings from "run the ram at 2 times to FSB" to, say, 2.5 (run the ram at 2.5 times the FSB), which is 695Mhz (your new FSB, 277, multiplied by 2.5). Okay not quite 800Mhz, but it will do for now.
Now you'd save this in the bios, and restart the computer. It's quite normal for your computer to turn off for a few seconds after selecting save & continue in the BIOS.
Once in windows, check your clock speeds, run Intel TAT, check your temperatures... is it all ok? Click the two START buttons and watch your temps rise... Too hot? Hit the STOP button... There's a problem with your cooling. Not too hot? Good, we can continute - open Orthos and stress test* [see footnote 2].
Whilst stress-testing in Orthos, keep TAT open (but make sure you haven't pressed START in TAT, or youll end up stress testing in two programs and probably lock up your computer =o] ), to monitor your temperatures.
Okay, all good? No errors?
Go back into the bios, add 11Mhz to your FSB. Make sure your RAM doesn't go over its rated speed (e.g. 800Mhz), unless you're willing to try overclocking your ram. Remember, if you ram does go over, you can fiddle with the RAM Multiplier to change its speed. Remember on a P5B etc you don't need to worry about this - because on a P5B you can set the ram speed and it won't change in relation to your FSB. Okay, now save and continue.
Monitor Temperatures. Stress test. Repeat this whole fsb "increase -> test -> increast -> test" until you're at a nice speed with nice temperatures. DONT GET GREEDY.
Okay, so now you have either:
- Got a nice clock speed and no errors in orthos, so you should leave the computer on overnight running orthos for say 8+ hours, and see if it came up with errors then.
- Or, you have got an error in orthos.
If you have got an error in orthos, something's messing up. It's nothing bad, and happens to a lot of people.
Firstly, you want to make sure your RAM is running at a good voltage. The Gigabyte DS4, for example, defaults to 1.8volts on the ram. But some ram needs up to 2.2volts to run properly! So go and stick an extra 0.2volts or whatever onto your vDimm.
Still getting an error? Make sure you're not overclocking your RAM.
Still getting an error? Well, the Core2Duos, if I remember correctly, run at 1.35volts (vCore voltage). By default, some motherboards put at little at 1.2volts into the CPU. Try putting a bit more voltages into that processor - but don't go over 1.4volts IMO, though some run theirs at like 1.5volts or more, it does start to get hot then.
The great thing about Core2Duos is that 99.9% of overclockers don't need to go over the default voltages to get 3Ghz
You could also try putting +0.1 or +0.2v on the FSB, or a bit more voltages on the chipset (MCH). Although I think FSB raises chipset voltage as well? So if you put +0.2 on the FSB, then +0.2 on the MCH, you're actually putting +0.4 on the MCH... Dunno, not 100% sure about that.
On my mates system, we has trouble in Test Drive Unlimited. After putting +0.1v more through the memory, it was fine.
DONE! You are now a qualified overclocker!
*1 SYSTEM MULTIPLIER or MEMORY MULTIPLER controlls the ram speed in relation to the FSB. NOT CPU MULTIPLIER, which controlls the processor speed in relation to the FSB.
*2 orthos is a good prorgam for stress testing. Some people say only test for a couple minutes between each step changing the FSB speed, some people say test for 30minutes each time. When I got my mates upto 3Ghz, we tested for about 45 seconds each time, and only did a *real* test when we were at 3Ghz - which it passed fine.
Please feel free to paste this text wherever you fancy if it's useful
It'd be nice if you said Furnace from OcUK forums wrote it though... Or just left this line in there.
Keep it at it's rated speed, you can overclock if you like, but even getting 900Mhz out of 800Mhz ram is probably pushing it 
