Originally Posted by Eureka
I've overclocked just the core, and the best I've managed is about 1150 on 1.38V.
Ok do this simple test. Download MSI Afterburner (go for 2.2.1 version I linked below).
1100mhz at stock voltage in Unigine Heaven 3.0 at 8xMSAA / Extreme Tessellation. Fix GPU fan speed to 85%. Record maximum GPU temperature.
1100mhz at "1.38V in Sapphire Trixx" with same settings. Fix GPU fan speed to 85%. Record maximum GPU temperature.
Report back GPU temperatures back to us. I bet your voltage control is not working.
Originally Posted by Eureka
So I picked up one of the VT 7970 GHz from the deal last week... looks like I'm OCing pretty poorly?
I can't seem to get it to stabilize past 1100 Mhz at any voltage. Stock is 1.175V. At 1100 MHz, around 1.225-1.250 will get it to run Heaven without any noticeable artifacts. At 1150 MHz, nothing will run artifact-free; I maxed out Trixx with 1.381V and it still artifacts noticeably. My GPU-z ASIC quality is 66.8%. Am I doing something wrong or did I just lose the silicon lottery massively?
I am going to asking the obvious -- How do you know your voltage is even working?
For example, you can move the slider in Sapphire Trixx but unless
you have enabled MSI Afterburner voltage unlock, it doesn't mean the voltage is unlocked. Out of the box, almost all HD7970 are locked in software without doing an unofficial MSI voltage unlock. You can still move the GPU voltage slider in Sapphire Trixx, and press Apply, but it won't do anything to hardware voltage in reality.
Did you actually check that your GPU voltage rises in GPU-Z (Sensor --> VDDC) under load or double checked that reading in HWInfo64? The fact that your GPU won't go above 1100mhz at any voltage is an indication to me your voltage is most likely locked.
Your ASIC is not low enough to not get 1100mhz. I've tested 3 7970s with ASICs of 59-63% and all of them hit 1150mhz with a slight voltage bump and 1200mhz at 1.25V. My guess is your voltage control is not enabled and your stock voltage of 1.175V in MSI AB/Sapphire Trixx (your target voltage only) is undervolting on top of this. In other words your actual Vdroop voltage with 1.175V is probably only 1.125-1.15V or even lower. My recommendation is to do an Unofficial MSI Afterburner voltage unlock (you'll need MSI AB 2.2.1
or earlier or need to import 2 .dll files into the MSI AB folder otherwise).
Under the heading [ATIADLHAL], add these 2 lines:
UnofficialOverclockingMode = 1
UnofficialOverclockingEULA = I confirm that I am aware of unofficial overclocking limitations and fully understand that MSI will not provide me any support on it
Adjust the voltage in MSI Afterburner, not Sapphire Trixx. Also, you may need to download Asus GPU Tweak to enable range enhancement for GPU clocks beyond 1125mhz. Your GPU would probably be hitting 90-100*C at 1.381V on air, not to mention this type of voltage is very dangerous to apply on air in the first place. Once you get MSI Unofficial voltage control working, go very very slow. Don't do anything like you just did with Sapphire Trixx, unless you want to kill your GPU.