Question: What post on here or somewhere has a good guide on how to under volt your card, hopefully the 7970. I will be using windows 7 32bit and SDK 2.6. I have read about using Catalyst or MSI afterburner to undervolt? Some people talk about just editing the CGminer config file. I would like to understand the purpose of undervolting beyond power savings (unless that is it) and what the correlation between the GPU Clock, GPU Mem Clock and the voltage is. Someone mentioned getting a card down to 130 watts each, how do I figure this math out? As Ludacris said, I want to know "how low can you go"?
In the the thread I mentioned above, the OP is using MSI Afterburner with overclocking mode 2 (and nothing fancy like bios flashing). The main advantage of undervolting is efficiency in terms of Mhs/watt, but you also get the benefit that the cards run cool and quiet. Power consumption goes up exponentially as you increase voltage, but hash rate does not, so you get a big gain in efficiency by undervolting. Mining is very light on memory, so you can also increase efficiency by lowering the memory clock without throttling the hash rate. How low you can go is partly a matter of experimentation - some cards undervolt (and underclock memory) better than others. My Sapphire 5850s are perfectly happy all the way down to 150 memory, but I have an XFX 5850 that freezes below 425 or so. But this doesn't mean that all Sapphires underclock better than all XFXs. 7970s are very efficient, but there will be variation depending on manufacturer and model. The XFX Black Edition, for example, will be more efficient than the standard edition. Basically, when you undervolt, you are still trying to clock the core as high as you can at the given voltage, so cards that overclock better at stock voltage will generally also overclock better at lower voltage and be a bit more efficient. GPUs are also more efficient at lower temps. In the thread I mentioned above the OP reports getting down to 109w per card (@550 mh/s) with water cooling.
