I am currently running a GTX 760 and i5 4670K no overclock. I have 16gb of ddr3 1600hz RAM that I just installed. My motherboard is MSI z87 g45. My PSU is HX750 by Corsair.
I recently tried to upgrade to a Vega 56 and 16gb of ram, at first it didn't work but after fiddling around my computer started and I was able to install the drivers. All was working fine until I tried to play a game. After about 5-10min the computer straight up powered off, not blue screen just turned off and turn on again.
However I simply cannot find a fix to this issue. I don't know what is wrong, it works find on desktop but running a game makes it shut off.
Normally when a computer shuts down without pressing any shut off buttons like Power or Reset it usually indicates a POWER or OVERHEATING or possibly software driver conflict.
I would install a monitoring software like HWMonitor or Open Hardware Monitor and see if any hardware is overheating. But most likely you need to configure your Vega56 using Wattman so as not to crash. Other Users had the same problem and needed to configure the Vega56 to prevent it from crashing.
This sort of issue is due to over current protection on the power supply being triggered. I experienced the same issue when I was using a power supply that is very sensitive to transient voltage spikes caused by the RX Vega. For me I fixed the issue by upgrading to a Corsair HX1200.
I would set the power limit slider in Radeon Settings, Wattman, to it's maximum, should be +50 on that card. See if that helps. This is IMHO, a common step needed to get many AMD cards stable under load when gaming. If this doesn't help. Try lowering the clock speed just a little bit at a time to see if and when it becomes stable. Likely the power limit slider will be enough.
If none of this works,
Run DDU from wagnardsoft_com from safe mode, see their instructions. Then reinstall the AMD driver while disconnected from the internet, this keeps Windows update from interfering with the driver install and settings, which is another current issue.
See if that helps. If it does not then I would see the contact page of the AMD site and open a support ticket. The link is at the bottom of the page.
If the computer turns off when starting a game it is not because of a driver or overclock problem. It is doing it because of over current protection on the power supply. Increasing the power limit of the GPU will only induce the issue more often. In contrast, to further prove my theory I suggest lowering the power limit by -50%.
Well I don't choose to provoke arguments, which your tone seems to do. Nor do I feel the need to prove anything to anyone. My advice has helped many people and been useless to others, as with any USER TO USER advice. This forum is for quick help from other users with the same or similar hardware experience. I would never deny anyone access to the advice your give, it may have worked for you and thus may potentially work for any OP. My 30+ years as an IT professional has taught me to never say NEVER. The increase of the power limit is an extremely well known fix for games that go black or hang. I never said anything about it being a driver or over-clock issue and only suggest an under-clock to increase the power stability ceiling, if and only if, the power limit slider max is not enough. Not even sure what you are talking about, certainly possible I didn't explain myself well enough for some to understand. When then happens to me I ask question to clarify not nullify another's advice. It seems that all of what you have issue with in what I said I never said and is what you inferred into it. If anything beyond the power limit slider suggestion (as that is normally needed and has been since the introduction of Wattman, for numerous Radeon products to get gaming stability) helps or does not help, at that point I would still think there is are HARDWARE POWER ISSUES. Either the card or the power supply at that point is likely to blame (yes there are potential other possibilities) is to blame. The suggestion to run DDU is to eliminate that nothing is corrupting the wattman settings and to start with a clean slate. This is how you eliminate variables to isolate an issue. You have to try to figure out what helps stability to get to the root of any issue. The OP is welcome to try and use whatever advice they get. If yours or mine proves to help, either way I am EXTREMELY happy they get back to gaming. There is"no one size fits all" approach, as from my place on the INTERNET I can only diagnose based on the information I have and prior experience. I have never touched the OP's machine and I am guessing neither have you. So yes any of us can potentially give wrong advice. If none of us help I hope they file an e-support ticket from the contact page or preferences in Radeon Settings and get some help from the AMD PROFESSIONALS. Good luck to you and thank you for trying to help others. That is what this forums is for.