Hi,
I'm having a problem running Mass Effect, World in Conflict and Company of Heroes.  Basically after running these games for a short while (a couple of minutes max) the screen goes blank, the monitor goes into stand by mode and it looks as though my PC has crashed.
 
I then need to cold boot to bring the PC back to normal.
 
Any help would be much appreciated I am running the latest catalyst drivers (8.7) and my temps seem good.

sounds like when the card starts to use some juice, it gets to a stopping point and shuts down...
What's your power???
 
I'm assuming this only reboots while gaming... Everything else works as should.. Am I correct in thinking this?
 
Also, check that all other components are seated correctly.. Ram, other pci/isa/etc....  whoa.. did I just mention isa... -lol- Never mind that one, if you have a new enough setup for the 4870........ But seriously, sometimes when a new card is inserted, other items "may" come slightly ajar....
 
 

Yes, we need the rest of your system specs, including the brand and model of PSU.
My first take is you have an overheating problem somewhere, most likely in an underpowered PSU.  If your GPU were overheating, you would most likely get other symptoms like artifacts.

Your Silverstone DA750 should have more than enough power for your system.
Do you have any problems with other games or applications?

Answering the questions above.
My PSU is a 750 - Silverstone DA750 should be more than enough I thought;
 
My system is otherwise completely stable passes memory, hard drive and cpu tests.
 
I'm also not overclocking;
 
Specs are as follows:
ASUS P5Q-E (1003), Lianli PC7PLUS, Silverstone DA750, Kingston HyperX KHX8500D2K2/2G 4x1GB CL5, Q9450 (at 3 GHZ), 2 x Seagate SATA 7200.11 500 GB (in RAID 1), 500 GB Seagate FreeAgent Pro, Zalman 9700 NT, 4870 with Zalman VF1000, XFi Fatal1ty ExtremeGamer w/ Logitech x-540, Samsung 2232BW, 2x ASUS 2014L1Ts , Abit Airpace PCI-E Wi-Fi and Vista Ultimate 32 SP1.
 
As above I note that I have an aftermarket Zalman VF1000 cooler installed.
Heatsinks on the ram chips are installed but unfortunately there weren't enough heatsinks for the voltage regulator chips.
 
I've just read this: http://forums.amd.com/game/message [...] adid=97493
 
Perhaps it is an overheating problem and the best option (at least until I can source additional heatsinks for the voltage regulator chips) is to re-install the stock cooler and see if that makes any difference.
 

Hi,
After quite a bit of mucking around I hacked off the back 1/4 part of the aluminium base of the stock cooler and bolted it to the card (with a thermal adhesive strip sandwiched between the aluminium base and the voltage regulators.  
 
On the aluminium base I affixed 8 blue Zalman heatsinks.  Seems to have improved matter but still not perfect.  The  Supreme Commander Benchmark now works without a problem.   World in Conflict still crashes but this time the monitor doesn't go blank and report no input.
 
I may have to look at the fan idea as above.  However unfortunately I don't have a spare connector for a fan on my motherboard.  I may just have to connect the fan to a molex cable instead.

Might be worth rolling back to 8.6 drivers, lots of people are experiencing display driver crashes with 4870's and 8.7 although normally you get a pop up message saying the driver has stopped responding and successfully recovered or something like that...