and the cpu undervoltage the guy did in that video. And used the settings for my cpu:
Powerlimit 1: 252w (did a -1w)
Powerlimit 2: 252w (did a -1w)
Icmax: 306A (dis a -1 on this one too)
Well, that's just the power and current limits, which you somewhat set to Intel's semi-arbitrary limits. You have to set them to what your cooling is actually capable of. I didn't see you mentioning the cooler, but for it to deal with ~250W (the maximum i would allow for any CPU), it would have to be a nice 360mm AIO. Most air coolers cannot handle that amount of heat. So with a lot of coolers, you can't set 250W, you have to set something lower. Which value, this you can find out by doing step 1) of my
Guide: How to set good power limits in the BIOS and reduce the CPU power draw. You would run Cinebench (R23 "CPU Multi" benchmark) which i link there, then you check in HWinfo what the temperatures go up to. You adjust the power limits until you can manage to keep it from entering the 90°C range.
So instead of relying on some Intel figures, which are not fitting well for most people's cooling, you can find ideal power limits for yourself. The 307A IccMax are usually ok, unless they kick in sooner than the power limits (meaning, you would see in HWinfo that the CPU Package Power = actual CPU power draw doesn't go near 250W), then it could be raised a bit, the limit according to Intel is 400A. But usually 307A should be enough. 306A vs. 307A doesn't make a difference.
But of course, then you do step 2), the actual undervolting. Setting power limits is not undervolting, it's what it says on the tin, it sets limits for the power draw that the CPU wants to observe, so if the power draw wants to get higher, it will throttle the CPU (lower the frequencies, so it can use lower voltages and have less power draw). But this is not undervolting, undervolting is when you keep the same frequencies at lower voltages. Power limit throttling, or any kind of throttling, will reduce the frequencies to have lower voltages. So in order to undervolt, you'd lower the AC Loadline setting on Gigabyte, like i mentioned before. I believe he showed that in the video too.
And I have 2 pci-e into 1 inside the gpu,
So your PSU does not include the native cable, where you don't need the 2x PCIe power -> 1x 16-pin 12VHPWR adapter?
Check if it includes that cable, and if it does, i'd use that instead.
One question: i saw people connect 2x 8 pins at for the cpu, I only have 1, is it something bad?
Every variant of the Seasonic Focus GX-850 has two 8-pin cables for CPU power (as 4+4 pin). So you can connect both. It only had advantages (apart from having to route a second cable), because using two cables halves the resistance and doubles the conductance.