[Solved] If i reduce the FSB frequency... what should i do to CPU voltage?

I'm a complete NOOOB at overclocking.. so plz help me out....

i have this strange kind of lock ups whenever I enable multiple cores and play a graphics intensive game.. (the more cores enabled and the more graphics intensive, the faster the hang) .... but if i enable just single core,.. NEVER hangs no matter what i do with it. I've been stuck with this problem since my purchase of this rig and I'm done with this problem... (i've checked this problem with various drivers, almost all Windows OS from xp onwards... its the same thing)

today, however i tried a new solution to it... I reduced the FSB of my CPU in the BIOS from 1333 to 1066 ... and put the RAM and CPU frequencies from [AUTO] to [LINKED] ...

i've played a game longer than the usual locking up time. .and it didn't lock up.... i guess that reducing the FSB has helped.. coz it has actually reduced by CPU's clock speed from 2.5 GHz to 2 GHz.

My question is... that after reducing the FSB do i have to do something to the voltage too ?? i mean... if the CPU is running at lower frequency due to the FSB, will the still higher voltage which is set to [AUTO] have any adverse effect on it..??..

plz reply soon.. and consider it again.. i'm a noob...

RIG:
Intel Core 2 Quad Q9300 2.5 GHz
EVGA 750i FTW motherboard
EVGA Geforce 9800 GTX+
Corsair XMS2 800 MHz Dual channel 2x2 GB memory

PS: if u need any more information... i can provide.. just ask.. plz help!

If I understand it right youre getting those lockups running at stock speed of 2.5ghz? You shouldnt be forced to underclock your machine in order to get it working properly, thats ridiculous.

So: basic rule of troubleshooting - one change at a time, than test. If you change several things at one time than you dont know what helped/what was the problem.

I suspect its more down to linked/unlinked memory and its frequency as a result than the actual FSB and CPU speed, but i dont have any experience with nVidia chipsets so I cant really tell for sure.

Anyway, as already said download CPU-Z , CoreTemp and Prime95. With CoreTemp check the VID(and compare against Core Voltage reported by CPU-Z while running prime Small FFTs test) also note the temperatures(at idle and when stress-testing with prime). In Memory tab of CPU-Z note Dram Freqency, ratio and timings(compare timings against those specified on the modules)

With that info we can carry on, of course if help is still needed.