p750zm instability and idk why? Help please!!

So I just got my p750zm and I was really excited. So i ran a stress test because i heard the cpu can run hot, and hot it ran. It would get up to 93 C in xtu's stress test. So i decided to underclock and undervolt. Here are the specs

cpu: 4790k
gpu: 980m
screen: 4k samsung 15inch
ram: 16gb 1600mhz
storage: c:500gb m.2 sata samsung 850 evo and d:1 tb 7200 hard drive

I undervolted first starting at -60mv core voltage offset. I then stress tested for 5 minutes, and then decreased in increments of -5mv. I got down to -100mv, and then It insta shut down, no blue screen it just restarted. The temps had been looking better at this point getting down to below a max core temp of 85C on normal for a 5 min stress test. I dialed it back and stress tested for 8 hours on -90mv and it was stable. I dialed back to -85mv just because I couldn't do a full 24 hr stress test, so I figured it would make it safe. However after a few days it insta shut down, no blue screen and restarted. So i dialed it back to -80 and then a day later it shut down, so I did -70 and then it did it again so then i decided to just underclock it from 4 cores to 4.2 to 4.0 and - 60mv. Then it shut down on me again.

The past few times I noticed that it shut down soon after I tried to access/write to my d: drive. Do you guys know what could be the reason for my computer shutting down, because I'm starting to think it doesn't have to do with underclocking or undervolting. Any help would be much aprpreciated.

Notes: Ive checked many other people who have the same cpu and laptop model and out of everyone who has reported about an undervolt without touching the cpu speed the smallest undervolt change I've seen was -80mv. Everyone else I've seen has been able to do more.

 

I'm working on undervolting my 4790K P770ZM now. Test with OCCT Max Fans (Fn+1). It will have slightly higher temps than XTU and is more stressful, which is good. My OCCT stable 40x multiplier (all four cores) is -50mV Core Voltage Offset -40mV Cache Voltage Offset 1.0270V Min - 1.0370V Max, .Max Fans, back propped up, ambient 28C°, Core 77C° min - 80C° max temp. My chip doesn't like lower voltages, it seems. Record your temps, offsets, TDP and voltages. I use XTU for my voltages and TDP, HWInfo64 for temps. XTU to undervolt.

My 40x -50, -40 passed my usual; POV-Ray, OCCT, x264 V2 three loops and finally, surfing/idle (for low stress stability) until the next day. I added these extras before low stress time, OCCT - Linpack tab w/ AVX, (83C°-85C°) XTU CPU Stress, XTU RAM just to be sure.

There's tons of info in the 15" & 17" owner's lounges. Check the 15" OP great work by @jaybee83 Also these posts are good for OCCT and undervolting in general.
http://forum.notebookreview.com/thr...-to-the-batcave.767105/page-771#post-10066106
http://forum.notebookreview.com/thr...-to-the-batcave.767105/page-778#post-10069636
@metacarpus results
http://forum.notebookreview.com/thr...e-to-the-batcave.767105/page-378#post-9930397

Look at jaybee83's chart, you'll notice as the multiplier goes up so does the voltage and the undervolt offset can, likely, be increased, to a point. I had the Freeze/Shutdown at -60mV core 40x, using OCCT. Don't worry about that. It's actually a good thing, to find stability and lower temps.

 

As a reference:
I got 85C in XTU stress test before any tweaking. This was with max fans and elevated on a cooler.
My initial -80mV undervolt has later been dialed back to -60mV because BF4 and Witcher 2 dissaproved.
Atm I´m going jaybees auto fan route and am running all cores on 4.1 GHz with -50mV undervolt. Max fans cut through my open headset quite alot.

Edit: When you underclock you might have to dial back on the undervolt offset. That´s probably why -60mV was stable for you at stock clocks but unstable when you underclocked.

And XTU stress test isn´t foolproof, it´s a good initial test. You need to also test your everyday software like various games and 20 tabs in Chrome. In XTU I´m stable at -80/-100 mV (core/cache) but as I said for everyday use I´m at -60mV.