Phenom II 550 Ocing

[Arcimbaldo]

Hey all after getting my pc up running stable i Decided to have a quick overclocking session, when i say quick i mean a few hours.
My specs
CPU: Phenom II 550 x2
Mobo: Gigabyte ma790x ud4p
GPU: Asus hd 4850
Case: HAF 932, replaced the side fan with 2 120mm scythe kaze ones
Ram: Ocz 800mhz gold edition

to start off with i had a go at unlocking the extra 2 cores. That failed as it refused to boot up so i tried it with 3 cores and it worked perfectly. Rather than only using the multiplier only i got that as high as i could and then worked on the fsb so i could oc the ram a bit more.

I then set the memory ratio to 5.33x giving me 1066mhz ram, gave it another 0.2v so it had 2.0v to play with. i then managed to get my cpu multiplier to 17.5x with an fsb of 207. This gave me 3726.3 mhz . This also made my ram run at 1104 mhz.
I could not get my pc stable past this point but was wondering how others have don eit, i would like to keep the 3 cores as i need them for dvd burning/converting.

Also no temperature program will now read my cpu temp, i presume because its been unlocked. however at the same settings as a dual it runs as 27 degrees on 100% load so im pleased with that.

So overall.
CPU: 3.73ghz
Vcore: 1.456
RAM: 1104mhz
Volts: 2.0

Any idea how i can get higher, i was looking for 4ghz but most people seem to be at about 3.8 with the 550's. So is this a reasonable overclock i left prime 95 on it for one hour and am about to do the same again.

Thanks for any help/advice on how to get higher

Arcimbaldo

EDI: Sorry i meant my multiplier is at 18x not 17.5.