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[GUIDE] How to Overclock your Skylake X


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Hi and welcome to my Skylake X overclocking guide (with pictures).
I'm using a Gigabyte X299 Aorus 9, but this is translatable, you'll just have to look in your bios for the equivalent settings.
This guide is not a simple 'bang up the multiplier' o/c and you probably should have some experience of overclocking previously.

First of all, Macs don't have good tools for monitoring or testing the overclock, so you need to do the overclocking in windows (sorry).

The o/c works great in Mac OS x though.
Another downer with OS x - HWMonitor doesn't work with the Skylake X yet, so you should be running the intel power gadget to monitor heat after the overclock.


WARNING: Do not try this if you have rubbish cooling. The i9 requires at least 360 of 45mm radiator space to get above 4.6. If you have air cooling don't bother unless you want to fry your chip.

At 4.8Ghz my CPU can get to 100 deg and that's with 1x420 and 1x360 rad.




The tools you need are:

(these are windows tools)

Open hwinfo and bring up sensors from the top menu bar. create enough columns to see all of the information you need. This can be done with an icon at the bottom with two blue arrows pointing out (picture to follow). Then open Aida64 and in the menu select system stability test.





In Aida64, select the stress CPU ONLY and start. Check your temps on the hwinfo then stop the test after a few minutes.
In Aida64 , select the stress FPU ONLY and start. Check the temps on the hwinfo then stop the test after a few minutes.

The FPU tests the AVX offset which will be important later.

The things you need to be monitoring in hwinfo are the temps for each of your cores and the VRM temps. Also note power (core #x vids) and the package power in watts.

Give Cinebench a run so we can have a baseline benchmark.

So, on to the overclock.
The following screenshots are for 4.8Ghz, we'll start with 4.5.

In bios we go first to the frequency settings.
Set the BCLK to a tiny bit above 100
Set the multiplier to 45
Set the XMP to profile 1 if you like.




Go to advanced CPU core settings.
Disable C1E, C6/C7, CPU EIST, Energy efficient turbo.
Leave the AVX offset and AVX 512 settings for now, we'll play with them later.

You can see the package power limits. I noticed that the limits of my CPU cooling came at about 320 watts, so I set the limit there. That way the wattage will never be greater than my cooling can handle. (This is a cool bit BTW)





Now to Voltage.
Vcore loadline calibration we can set to Turbo.




Moving right along,

Go to CPU core voltage control.
This is a cool bit.
Set the Vcore to normal and offset to +0.050
Set the Mesh voltage to normal and the offset to +0.31
This'll set CPU volts to about 1.27 and mesh to about 1.2 volts.
This should be good for 4.8
If you find the volts in HWinfo are different, simply tweak the CPU offset to make it right.
If you only go to 4.5, you should be able to sit around -0.050 offset or more! Check and see, I had a stable 4.5 at 1.1 volts.




Now get into windows (yes I know, I'm sorry) and we'll do some testing.
If you can't get into windows, go back to bios and lower the clock, although this is unlikely.
Run up hwinfo and aida64.
test CPU only and note the temps.
Test FPU only and note the temps.

CPU should be fine unless you have bad cooling.
FPU is likely to be higher, but if we look at hwinfo, we need to avoid the throttling - it'll show you this in red. If it doesn't throttle it's ok.
At this point we can run Cinebench to see if we have an improvement.
Run it after every boot, but note that it makes the CPU hotter than the Aida64. Try not to freak out and don't let it get above 105 degrees. Do a wee practice on how to stop the benches quickly.

Now we just go back to bios and keep bumping up the multiplier. We might have to bump up CPU voltage offset as well, until we get unstable or too hot or no longer see any benefit.

Now, the AVX uses a heap of power and can't be at super high clocks.
The AVX offset we see in a screen above is the downclock. so if the clock is 48 and we set AVX to 5 and AVX 512 to 6 (512 should always be 1 higher than AVX offset), then when AVX is running on the computer, the clock is really either 43 or 42. It's gone down by that amount we set.
We decide how much that offset should be by running Aida64 CPU, then FPU (never both together), and when our FPU temps get to high, that is 1 above the max clock for AVX.
Got me? So if we test at 4.5Ghz and it's sweet, then 4.6Ghz and FPU bench temps are too high, we set the offset to 1 and 2 (2 for 512).
If we move on to 4.7, we set the AVX to 2 and 3. We move to 4.8 and it gets set to 3 and 4, and so on.

Now because OS x doesn't use AVX yet, I think, I just cranked the offset up until the temps in Aida64 both CPU and FPU were the same.

I'll attach my config so you can have a look. There's nothing special in it.

Other stuff we can do:

A lot of people set their CPU mesh ratio to 32, it only speeds up benchmarks though.

A lot of people set their CPU VRIN External override to 1.9V - it helps to stabilise an overclock.


DON'T use Prime95 unless you set your min and max FFTs to 96 or you have a death wish.


And done!


Kick windows out, boot up the Mac and enjoy :)



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