GPU output suddenly black screens (hard crash)

[ruddyhell]

I'm in need of some help here.
Its coming up for the christmas holidays and gaming is high on the agenda.
However my graphics card has decided to drive me mental (atleast I think its the gpu).
So after around 10 mins in for example shogun 2 or anything that puts the graphics card under load before the temps can get to above 60/70C it crash's to a black screen and sound can be heard for a few seconds and then a Hard reset must be done to gain graphical output.
Now from what I can tell the 6970 is still outputting but its output signal is just blackness (monitor still sees signal).
I have mem tested with no errors and with a change in power supply I keep getting the same black screen crash.

Is it the gpu? is it boogered?

Specs:
Win 7 64
HIS ATI Radeon HD 6970 2048MB GDDR5 PCI-Express Graphics Card
Intel Core i7-2600K 3.40GHz (Sandybridge) Socket LGA1155 Processor - Retail
MSI P67A-GD65 Intel P67 (socket 1155) DDR3 Motherboard ** B3 REVISION
Samsung B2230H 21.5" Widescreen LCD Monitor - Glossy Black
Corsair Vengeance 8GB (2x4GB) DDR3 PC3-12800C9 1600MHz Dual Channel Kit (CMZ8GX3M2A1600C9)
XFX Pro 750W Core Edition '80 Plus Bronze' Power Supply
Western Digital Caviar Black 1TB SATA 6Gb/s 64MB Cache - OEM (WD1002FAEX)
Hitachi Deskstar 7K1000.C 1TB SATA-II 32MB Cache - OEM (0F10383)

 

[wazza300]

what dram voltages are you using for your pc memory? test by downclocking the gpu memory freq by 200mhz and then try/see if it hard locks

 

[ruddyhell]

cheers for the reply.

yeah still hard locking at underclock.
dram voltages are sitting at 1.4888v.

I'm slowly losing my mind........If I try another card (5770) and it does not hard lock does that confim its the 6970?

 

[wazza300]

your dram is abit low imo,id use atleast 1.55v

not really the 5770 wont push your system like the 6970 will,it seems memory related to me,either the gpu or pc

i had same issue with a 5870,downclocked the memory freq and it ran trouble free

 

[ruddyhell]

Well its seemed to work.......took the memory of the gpu down by 205 and increased the dram to 1.55 like you said.......and all seems good.

Thanks very much for your help!

 

[wazza300]

just keep testing now,see how far you can push gpu memory clock upto original clocks,it simply might have been pc dram voltage too low

 

[ruddyhell]

ok so as I was reading this thread and then 6970 black screened again
so I thought may as well try the 5770 waped it in and done the whole driver uninstall/install thing.
The card was running at a 17C idle so thought test the default clocks and overclock it (just as a test) so kept the clocks all default and ran test clocks in CCC....bam black screen.

so.......what could it be???????????? Hard drive? motherboard?

 

[wazza300]

try with 1.5750v dram voltage,and look for cpu/vtt or cpu memory controller voltage and try from stock 1.05v to 1.1v

maybe 1.08v and test again,its something simple like voltages or driver issue