Constant restarts during demanding games - power / PSU issue?

tl:dr, consistent straight restarts after about 20 mins of demanding gaming in 4K on watercooled system, almost stable when underclocking the graphics cards, suspect insufficient power

Hi,

I'm getting consistent restarts when playing demanding games (or streaming them through twitch or youtube). This usually happens about 20 mins in to playing.

There is no BSOD or hang, generally speaking, it's just a straight restart.

I've already been on the phone to scan about this as I initially got a 'power surge error' where the X99 board had activated its power surge protection. On the advice of Scan, I disabled this in the BIOS, but unfortunately the restarts still occur.

I've loaded the non-overlocked profile 1 in the BIOS and set the graphics cards to no overclock too in EVGA PrecisionX. Issue still occurred.

The only way so far I've managed to get it reasonably stable is to actually underclock the graphics cards by dropping the power target under 100% in EVGA PrecisionX. I also dropped the clock speed and memory clock to negative values. This allowed me to play GTA V in 4K with all the bells and whistles for 2 hours with no problems.

Even when it was stable though, trying to stream demanding games would cause the same error (I'm using OBS to stream).

I've been monitoring temps, usage and power draw (along with the other usual factors) in a variety of applications including MSI Afterburner, GPU-Z, HW Monitor and of course, EVGA PrecisionX. I've been stress testing it mostly with two of my most demanding games in 3840 x 2160 - GTA V and Shadow of Mordor - the latter with the HD texture pack installed. Also been testing the new Mad Max.

As this is a watercooled system, temps are predictably fine, they don't go above 60 under load. GPU-Z's log didn't show anything particularly out of the ordinary either (I can attach these later if you like). Power usage and GPU load are predictably high but nothing much over 80, depending on which GPU overclock settings I used.

I think this may be a power problem, as the straight restart behaviour and my initial 'power surge' problem seem to point towards that more than anything. So I'm guessing (so far) that it could be:

A. A faulty PSU

or

B: Insufficient power


While I understand that an 860 watt PSU should be sufficient for my system, I'm concerned that maybe it isn't.

I made a fair few modifications to my system from the original X99 Cyclone.

While I realise that my extra drives and USB peripherals etc. shouldn't take up much more power, the overclocking certainly would. I've looked at a few power calculators today, and while some of them should be taken with a grain of salt, it looks like my power levels are running dangerously close to the 860 watt mark, and that's without overclocking.

In addition, when I first booted up the system after taking it out of the box I got the 'overclocking failed' error, 'press F1 to run setup' on post. A restart fixed it, but it made me a bit concerned about the overclock.

I've also noticed that the twin Titan Xs are the superclocked versions and was wondering if that made a difference to power draw or to the way they are adjusted in EVGA PrecisionX.

Hope you can help

Thanks

Simon

p.s. apart from this issue, the machine is a dream, I'm running everything in 4K/UHD at 60 fps :)