How to diag a faulty AMD/ASUS HD8760

[cognus]

in need of more experienced wisdom here.
I have a asus m51bc so called "essentio series" minitower that came with a asus branded OEM-only radeon hd 8760.
it does not work well. never has. has seen little use since new in 2013 because of the problem i'm trying to solve.

basically under even a moderate load the graphics card bails in an ugly way. pull the card and put in a known stable sub; in this case a humble GeForce 640 card, the system is bulletproof under heavy load. so the underlying hardware etc seems ok.
the power supply is around 450W and there are two dimm's, 6gb+6gb, and a low power wifi card in a pci slot. the processor is one of the amd fx 8-core.

how do I determine if the 8760 is at fault? benchmark/diags suite? which? source? link?
what would you suggest to try to bring the card into tolerable limits, assuming the card is not technically "faulty" ??

 

[TairikuOkami]

GpuTest - Cross-Platform GPU Stress Test

What brand is your power supply?

 

[popeye]

Can you try the card in another machine?

 

[cognus]

Tari, that is the one I settled on. some of the others out there load too many variables into the software mix so I deferred those and used the open gl one below.
as to the other suggestions - I have another sys coming in over the weekend for a job and will try the card in it - vastly different system - all intel, quad i5 etc..
The power supply I did not take note of brand - something asus uses in pre-builts. it has little load on it. watching the monitoring widgets, no stress.

software-wise I had the system driver/remnant free on 2 separate runs : the card is basically a radeon 7770 rebranded - I do not know what is done to the video bios itself, whether it is 'normal' or asus-tweaked for some reason. not many of these are out there in the wild so hard to get info and Asus isn't supporting well [there is no driver for the card on the machines download page, and not much else for that matter]. I ran it with the AMD Catalyst full suite, whereby it comes up as the HD 8760. fails with even the lightest "benchmark" suite, fails of course with a lightly loaded stress test. it never completed any single test run. Unloaded all that, cleaned out all the AMD remnants again until there was nothing left but the MS generic vga. Next run I fetched the driver windows update has for it: it is the generic WDDM for windows 8.1 - comes up as HD7770. Ran benchmark again and got the hard crashes. I note that the longer the card stayed powered up, the artifacting changed/worsened. Whatever was amiss was causing a bizarre retention of error such that, on restarting the system [which had to be shutdown the HARD way... btw.. the power-button shutdown was ineffective] during POST the display was corrupted with big vertical noise bands painting the display, well prior to Windows even loading. These would clear if one bleeds charge off the capacitors completely, but would retain through mere power-cycling or restarts.

Only 2 system BIOS's have been published for the box. The first one seemed to indeed have some sort of Video tweaking embedded, as when I installed the 'reference card' nvidia 640 GT I got a message from BIOS saying it had altered the video setup to avoid damaging the card: "Press F1 to continue; F2 or DEL to enter Setup" - well, the latter is of no value since there are NO video settings available in the Advanced section of the Setup UI. none whatsoever. However, after updating to the later BIOS, I got no such message when switching cards.

The Nvidia 'ref' card sailed through all sorts of benchmarking and stressing - no issues whatsoever.

I don't know what else to do. I hate to assume the card is defective without a precise test or root-cause but it shows no stability under any circumstances I could muster.

GpuTest - Cross-Platform GPU Stress Test

What brand is your power supply?