What does changing voltage on cards do?
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Hey guys,
I’ve been slowing overclocking by two Sapphire 7950 dual x cards since I got them installed with risers (nice air gap). Have both set at 1100 Mhz core / 1150 Mhz memory. Getting 0.65 Mh/s from each. 73-75c at about 50% fan.
I’ve noticed one has a higher voltage than the other. one has 1.256v, while the other has 1.169v. Both seem to perform much the same.
I believe I need custom firmware to change the voltage?
But what exactly does changing the voltage do? I can’t find much on this topic. I’m assuming it drops power consumption, and maybe the temp somewhat? I want to get the most hash/s out of my cards, but won’t be complaining if I can also drop the temps / power usage.
Cheers guys.
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It does. Ohm’s law states that work is equal to voltage times resistance, so if you lower your voltage, but you keep the resistance the same (same number of computations per second in this case) you do less work to accomplish the same thing. This results in lower temperatures, which has a direct impact on longevity of your hardware.
Alternatively, raising the voltage can increase overclocking performance and allow for higher stable clock speeds, but you pay a price in longevity if you don’t take some precautions to cool the damn thing.
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Cheers Kevlar, much appreciated!
Lower power and heat are always a plus, just as long as it doesn’t mess with my hash rate!
Now just researching changing voltage in BAMT. Think I’ve found a bios if my voltage is locked. Thanks again.
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I thought my sapphire 7950 was voltage locked because nothing would work…then i tried using sapphire trixx and I could change them there. Each card runs within a certain % tolerance at any given clock rate. Too much power and you blow it up and too little and it wont work properly either. These cards have different voltages because their tolerances are slightly different. One needed a little more oomph to get the same job done.
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[quote name=“RIPPEDDRAGON” post=“40895” timestamp=“1386387296”]
I thought my sapphire 7950 was voltage locked because nothing would work…then i tried using sapphire trixx and I could change them there. Each card runs within a certain % tolerance at any given clock rate. Too much power and you blow it up and too little and it wont work properly either. These cards have different voltages because their tolerances are slightly different. One needed a little more oomph to get the same job done.
[/quote]Cheers for your input! Mine have the sapphire trixx (looking at the box), but I’m running BAMT so not sure it’s much help. I tried changing the voltage settings in cgminer to no effect. I think my next option is trying custom firmware (not over the moon about that), as the last post in this thread say: https://litecointalk.org/index.php?topic=3358.15