Hi,
I am trying to OC my brother gaming computer, the Q9550 runs stock at 2.83Ghz with 1333.3Mhz FSB at 350MHz BUS  at 1.28V Vcore 1.20V VTT, 1.30V NB voltage, 1.5V SB voltage
RAM is a samsung DDR2 800 PC-6400 6-6-6-15 1.90V DIM voltage.
I hope I put enough information here, all that is with out manipulation.
 
Now I increase FSB litle by litle but I can get it stable at more then 1493Mhz = 3.12GHz CPU speed, yea I unlinked the RAM so I making sure I am running it at 800Mhz, I increase Vcore to 1.4V and NB VTT but nothing seems to make it stable and I keep failing on PRIME95 with a FATAL ERROR possible hardware failure message.
any Idea why? and what I can do to make it stable?
 
oo and yea this is the System specs:
Case: Thermal take I am not sure on model
mobo: ASUS P5N-D
CPU: INTEL Q9550
CPU cooler: Thermaltake Contact 30 with 120mm blue LED fan
RAM: SAMSUNG DDR2 800 PC-6400 6-6-6-15 2T  1.9V
GPU: 2x EVGA GTX285 in 2 WAY SLI
PSU: CORSAIR TX850W 
wireless card not too sure the brand or model

beaconpcguru

Why arent you increasing multiplier first? Never mind the fact that you should be able to do 400 (1600) FSB x 8 Multi = 3.2ghz rather easy... why not start there and move up. And set voltages to auto across the board... shouldnt even need to up the volts to do that...  Lin-x or Prime it then.. see if it passes... then post back if your stable with that

you right, I read every article on OC forum, Toms hardware and it should be hit 1600FSB (400BUS) X 8.5 = 3400MHz with out much effort, but I think my brother has a chip that reaches is maximum stable FSB OC at 1460 (375) x 8.5 = 3187MHz,
The way I am OCing it now is, I have lowered the multiplex to 6x (minimum this mobo offers) and just increasing FSB so that I deal with core clock later, I wanna see what is the max FSB this chip can run and it seems to hit a wall at 1460 with a lot of VTT 1.4V (max safe 24/7 VTT for those 45mn chips) so I think the chip is well shot since my brother ran it with the 20% AI overclock offered by the ASUS OC UTILITY, and he ran the computer with massive crashes and BSOD for a year, now that I look the AI OC was pushing 1.5Vcore for maintain stability at 3100Mhz, a litle too much since the safe Vcore should be no higher then 1.4V, and he never really look at temps and anything and I find out by putting real temps the is cores was running at 80C and more so I think he killed this chip, well I am going to OC it at higher it goes with 1.4V max on VTT and Vcore, and of course passing 20 tests on IntelBurning test and then 12hr on Prime95 when I reach the higher OC to make sure and I go from there.
 
Thanks man 

Xazax310

Just FYI i've ran into this a few times, it could be a FSB wall where between a range say 460-480 you cannot overclock the processor no matter what, try setting your FSB to 500/520 or higher(skipping it) then see if it boots and is stable, i've ran a Q9550 personally in an ASUS rampage X38 at 4.0Ghz 24/7(under water) so i dont see why such a minor increase is making the processor unstable

I tried FSB 1600 (400) at a lower 6 multipler and it don't even boot on Window, I raised VTT up to 1.5V (way above safe) and still freezing on a window logo wile booting, then I tried 1650 and wouldn't even go to the window booting logo, the highest for booting into windows is 1500 but not stable, I think this chip just doesn't have it. I know is not the RAM I set the ram unlinked at 800MHz stock ran 8 pass on memtest86 and all good, so I know is a CPU wall.
current working setting:
FSB: 1470 (367) X 8.5 =3117
RAM: 400 11:12 at CL6-6-6-15-2T
RAM V: 1.91V
HT voltage (VTT): 1.4V
NB voltage: 1.32V
SB voltage: 1.50V
Vcore        : 1.3125 (1.24V effective)

If you remember your setting I can give it a shot. I still don't understand why it needs all that VTT for find stability at 1470 (367) when I saw in forums people use to OC this thing at 3.4 easy with the same VTT I am using, I think my problem is this ASUS P5N-D mobo with 750i nvidia chipset, I read this mobo is good on OC dual and not quads, but I should of had no problems to reach 1600 (400), so I don't know