Which part of my computer is breaking? [With Video]

sleater

First, spec:

XFX ATI Radeon HD 5850 1024MB GDDR5 PCI-Express Graphics Card
Intel Core i5 750 2.66GHz (Lynnfield) (Socket LGA1156)
Gigabyte GA-P55A-UD3R Intel P55 (Socket 1156) DDR3 Motherboard
2x Corsair XMS3 4GB (2x2GB) DDR3 PC3-12800C9 1600MHz Dual Channel Kit (CMX4GX3M2A1600C9) (8GB total)
Corsair Hydro H50-1 High-Performance CPU Watercooler (Socket LGA775/1155/1156/1366/AM2/AM3)
Antec 300 Three Hundred Ultimate Gaming Case
Windows 7 64 on some kind of OCZ SSD I bought late last year

I've had it happily clocked to ~3.8ghz since I got it last August, and for the last few months at 4ghz with the VCore tickling 1.38, the temps never break 40c (that cooler is obscene). It has been a rock solid build, probably the best I've had. But over the last few days, it has been playing up.

I managed to get a crappy vid of it failing:

[vidurl=http://www.youtube.com/watch?v=nF66Ivtjaow]SHAZAM[/vidurl] - I know it LOOKS like a vid card dying, but would that really cause the following boot up problems?

After this crash, I couldn't even see a bios screen on rebooting. Fans would spin up, but even resetting the CMOS would do nothing. I persevered, tried shuffling the RAM, taking some sticks out and resetting again and again, eventually I got it going. It ran fine for a while then glitched out and crashed again. Repeated the process and got it going again (after an hour or so of it just flat out refusing), but I don't like to just sit on problems so I fannied around with the RAM sticks and it refused to boot again. When it does this, the Phase LED lights on the mobo max out and sit there (this should only happen for a few seconds while booting, IIRC).

Sigh. Again I spent an hour moving stuff around and resetting until it booted again (I honestly have no idea what I do that makes it work), it's now sitting upstairs in Crysis 2 while I see if it falls over.

It's basically running at optimized defaults, only at 4 of the 8GB of ram, no mega clocks or voltage changes. Nothing, not even the graphics run hot, at all. If anyone from the video or the symptoms can even point me at what this might be, it'd be massively helpful. I don't want to have to build a whole new computer. Again.

edit: in the vid, the computer doesn't actually reboot or turn off, the fans are still running etc.

LoneIgadzra

Damn, that was just happening to me. Seemed related to memory controller, since I got it running pretty consistently in single-channel mode.

Eventually I RMA'd the motherboard, and I'm pretty sure they sent me mine right back instead of a replacement because I recognized the dust patterns and fingerprints but now it works perfectly and ASUS didn't include any notes at all as to what they did so I dunno WTF.

I determined that neither of my memory chips was broken to my satisfaction by simply going down to one in a working slot and then swapping to the other. Also did a ton of video card tests and temperature monitoring, and eventually decided that that wasn't the issue since I was having the black screens even while not running games.

citizen059

Does the system initially fail when you're playing games? Or do you get this when doing things that aren't graphically intensive?

sleater

I first noticed the flickering it was doing (in the video link) in games, then after a couple of crashes during Crysis 2 it would do it on the Windows Login screen, on the desktop and while doing nothing graphically intense at all.

That was even at default clock settings, too.

I left the system doing a 100% load 3D/Cpu and Ram test for 4 hours while I was out today and it was still going when I came home. As far as I can see now, it's working fine, but then it felt fine before. There is something in there that is potentially causing problems, but I really have no idea what the symptoms point to.

citizen059

I don't suppose you have another video card handy?

Failing video hardware can prevent a PC from booting up, so you could get those issues if the video card is going.

sleater

I have an old 4850 in the office which I will try should the system fall over again. I'm currently in the process of running 3DMark 11 and Vantage at whatever kind of extreme settings I can to see if I can get a reaction.

Failing that, I'll clock it back up to 4gig and rag the hell out of it this weekend.

sleater

Vague update: Ran 3DMark Vantage and 11 a few times on extreme settings at 4Ghz overclock (I got bored) and it seemed stable. Crysis 2 also didn't glitch or freak out so I tried upping the GPU clock and RAM, it started to crash almost instantly so I Alt F4'ed that bitch. I stuck it on a slight underclock just to be safe until I can get the old 4850 and experiment.

Guess it could be the graphics card after all, even if it's not running hot. Weird, but not entirely out of the ordinary for my ATI experiences.