Try power management menu for C1E and EIST / speedstep. These options basically down clock and volts your CPU to the lowest multi to save power.
C1E does it at a halt instruction to the CPU, and EIST (Enhanced Intel Speedstep Tech) does it in finer increments and below certain CPU workloads so is a bit more intelligent.
I'd recommend using it to be honest as it all helps on saving electricity cost if the computer is idle or not working very hard. Whenever any workload is put on the CPU is just will instantly use the higher multi clocking back up to your high clock, i.e.
300 FSB x 6 = 1.8ghz
300 FSB x 9 = 2.7ghz
A lot of people on forums will tell you to turn it straight off when overclocking as it can affect stability. Whilst this is true - it can - it depends if you want to run with it on or not. What some people find is that speedstep can affect stability at idle, as some motherboards don't compensate for your overvolt when running down clocked at the lower multi. I have this problem currently with my quad core q6600. If I turn speedstep on and keep my clock at 400 x 9 = 3.6ghz I can pass prime tests overnight and run stress tests all day long and it will pass fine. But then occasionally at idle it will lock up because even running at lower 6 x multi it's still 2.4ghz which uses the stock 1.225 vcore; it would normally be 300 x 6 = 1.8ghz (I think)
So I either turn speedstep off or just wind my clock down to 3.51ghz and all is good.
You also need to account for vdroop. This is where the voltage you set for the CPU in the BIOS might be say 1.45v but in windows monitoring utilities they are reported as say 1.39v under load. This is due to vdroop and sometimes you have to up the voltage to compensate.
You also mentioned northbridge voltage. You may well need to up that to maintain stability. In fact, this looks a particularly good candidate for your stability issues, as this will affect memory stability as well. check you rmemory is running at the right volts. Too many volts can often be worse than too little. Try slackening the timings and keeping it running below spec with multipliers to eliminate the memory being the bottleneck if possible. i.e. Find out the highest your CPU will go first.
I have a e2180 that just came out of my PC waiting to be sold actually. It did 3.4-3.6ghz but I ran it 24/7 at 3.2ghz with 1.35v I seem to recall.
Hope this helps.
