I recently built my brother a computer for his birthday and the specs are:
E2180
Gigabyte GA-P35-S3G
2GB Corsair pc-6400

Now he asked me to overclock his PC to 3GHz, i've seen people overclock E21x0 chips very well, but this chip doesn't want to go above 2.5GHz! Any ideas?

I'm not very used to the Gigabyte bios mostly.

First thing to remember is its a 65nm chip. Meaning you can be more aggressive with 24/7 vcore. 1.45 should cater for 300fsb, but that's chip dependant. You can go higher.

Other than that keep the ram at 800mhz, use the NB straps wisely if you have control over them and keep tweaking.

shamelessly ripped from Custom PC issue 55 page 109 :D (E2140, but still still work with your chip, just means using the lower multiplyer and high FSB, adjust as you see fit)
FSB 375
CPU Clock Ratio x8
System Memory Multiplyer 2.40
+0.1v to RAM
+0.1v ro FSB OverVoltage Control
CPU VCore to 1.5v

My friend done this (I read this out to him over the phone :D) and it worked, as said a lower FSB that mine will be better and use your higher multiplayer

1.5v? Are you nuts dude I got an E2140.. 375x8 giving 3000MHz, at 1.35v!

1.4375v for a 100% OC, lower that to be honest.. it should be 100% stable at 1.35v if not lower.

Also, no need to up the RAM voltages if you're on a 1:1 FSB:DRAM divider, it will be running below stock if you're on DDR2-800, it will be running at 750MHz so no need to up your volts!

FSB overvoltage.. leave that as low as it can be (in my case) and it is 100% stable.. over 10 hours of Stress Prime 95.. so I think my point is proven. Not all voltages have to be raised, they only have to be raised when and where neccessary!

1.5v? Are you nuts dude I got an E2140.. 375x8 giving 3000MHz, at 1.35v!

1.4375v for a 100% OC, lower that to be honest.. it should be 100% stable at 1.35v if not lower.

Also, no need to up the RAM voltages if you're on a 1:1 FSB:DRAM divider, it will be running below stock if you're on DDR2-800, it will be running at 750MHz so no need to up your volts!

FSB overvoltage.. leave that as low as it can be (in my case) and it is 100% stable.. over 10 hours of Stress Prime 95.. so I think my point is proven. Not all voltages have to be raised, they only have to be raised when and where neccessary!

The fsb does need raising since he is stuck :p It depends what board you are on etc, there is a lot of variables.. Your point about vcore sounds correct though :)

Yeah but increase it gradually, do not go by a book as every CPU and motherboard is different and handles differently!

Thanks for the replies, I shall be trying it tomorrow :)

1.5v? Are you nuts dude I got an E2140.. 375x8 giving 3000MHz, at 1.35v!

1.4375v for a 100% OC, lower that to be honest.. it should be 100% stable at 1.35v if not lower.

Also, no need to up the RAM voltages if you're on a 1:1 FSB:DRAM divider, it will be running below stock if you're on DDR2-800, it will be running at 750MHz so no need to up your volts!

FSB overvoltage.. leave that as low as it can be (in my case) and it is 100% stable.. over 10 hours of Stress Prime 95.. so I think my point is proven. Not all voltages have to be raised, they only have to be raised when and where neccessary!

Tried that didn't work :(

Tried all sorts of things, it just wont boot.. Even if I raise it to 2.5GHz.