Spec: i7-4790k, GB Z97X-SOC, 32Gb DDR3, GTX 1070 3xHDD, 2xSDD, sound card (creative recon 3d), wifi card, usb kb/mouse, noctua d14 cooler, a couple of case fans, antec EDGE 750w PSU. Backhistory: This system has been somewhat unreliable since I built it ~2 years ago. The 4790k was overheating in a fraction of a second, until I disabled turbo boost, dialed down the processor current limit from 1000A to 105A, and set core voltage to 1.105v (following suggestions in a Intel forum thread). Since doing that it's been 'effectively' stable, I've done plenty of machine learning, and plenty of gaming, even triple screens @ 1440p, although it still wouldn't pass a prime95 stress test. Fast forward to today... The system randomly resets. No error. There's nothing interesting in the system logs (just the 'oh hey, your system didn't shut down properly last time' logs). It seems pretty obvious that it's a hardware issue of some form, rather than a software crash. It almost (not quite) exclusively happens when the system is under heavy load Examples: - DX:HR kills it in single digit minutes. A few months back I could play it indefinately without issues. - Aven Colony dies in minutes on max settings, but can last over an hour on minimal settings. Just 2 days ago it was fine to play indefinately on max. No software changes between then and the problem starting. - Low use of the computer (browsing, spreadsheets, etc.) works 100% fine. Gaming at low settings instead of ultra seems to reduce, but not eliminate, the problem. Halving the CPU multiplier from 40x to 20x didn't help, so despite the history, I'm leaning towards thinking it's probably not the CPU. A cat bumped heavily into all the cabling at the back very recently, but I think that's a red herring. I pulled the 1070, took a good look, and reseated it just in case. No effect. Visually checked the power connections to the mobo, couldn't see anything that looked loose. I've been watching the temps. CPU and GPU look quite reasonable right up to the moment of reset (i.e. logging at 200ms intervals, no nasty spike logged before crash. Neither GPU nor CPU going much over ~60^C, which is quite tolerable.) It seems quite hard not to blame the PSU, but without a suitable spare, I'm not quite sure how to go about verifying this. The PSU *ought* be to fine - it's a premium-ish model, 2 years into a 5 year warranty. Power calculators suggest 500W is enough to drive this system, and it's rated at 750W, which is a pretty hefty margin of error. 6 months ago I had a much more power hungry 980Ti in this system without issues. It's been a long time since I troubleshooted hardware... Any advice, before I have to descend into the pit of semi-randomly buying replacement parts until the problem vanishes...?