So i am trying to get my i5-750 to 3.6ghz which should not be to difficult, but I have no idea what voltage it should be at...
current setup is
i5-750 oc to 3.6ghz at 1.27 volts which is probably to high...
1600mhz ram at 1.60v
I don't think you should need quite that much voltage. Something like 1.2 - 1.21V IMC and 1.28V Vcore should probably suffice. Of course, all systems are a little different so you might currently be at the minimum. Hard to say, only testing will tell.
How are your temps currently?
Also, just an FYI, I prefer to use Intel Burn Test as it can be much quicker to determine stability, or at least instability. I still think a good overnight Prime95 Small FFT run is a great way of determining stability overall but when making small voltage adjustments, IBT can help make things a lot faster.
Also, another FYI, it is potentially possible that RAM is causing the issue, depending on your settings. If you're at rated speed (guessing here 1600mhz) then it shouldn't be that but I don't know your exact baseclock or speeds so just guessing.
I'd also try using EIST, C1E, and C States if possible just because they're good power saving features but if they cause instability then so be it.
Well, right now I'm running my i5 750 at 177 base clock, with turbo boost enabled (3.7 to 4.2ghz). I disabled LLC for turbo OC because I like the way it gives less voltage with all 4 cores active, and then a little more voltage at the higher clocks (with less cores). I used to have LLC on for this, but turning it off actually dropped temps a couple degrees once I got it stable. So, with LLC off I'm running (iirc) 1.38V Vcore and 1.21 VTT/IMC - but remember that my load voltage is less. Actually on 4 cores it's only about 1.29 or 1.3V. Anyway my temps are actually only about 70C max as well with a Zalman CNPS10X Extreme cooler (and I put a Scythe Slip Stream 120 PWM fan on it because the PWM control on the original fan stopped working).
Well, bottlenecking is a phrase some around here really dislike (with good reason, actually). The answer is it will depend. For most games you will be fine, for others, no amount of OCing will help. But short answer - yes, 3.6 GHz will be plenty in most graphically intensive games.
Adding more monitors will eat up any GPU headroom far, far faster than CPU usage.
Generally speaking the more demand on a GPU the less and less you need to worry about CPU clock. If you run low resolution you can bottleneck your cards, but running 3 monitors there's no way you could even dream of bottlenecking them. If you want you can run a simple test...
Run single card at, oh, 720p in a FurMark benchmark. Then run a second card at the same low resolution. Now do it again, at 1080p or whatever your monitor's native resolution is. I did this and found the increase in FPS at low res going from a single to crossfire 5850s was about 5fps gain lol. At 1080p, it was a 90% gain. FurMark runs a single thread, so it's going to show bottlenecks a lot sooner but even then at 1080p the CPU bottleneck was probably gone (considering 90% scaling is very good).