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7970 different voltages
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Dravonic
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Videocard: VisionTek 7970 3GB
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Default 7970 different voltages - 02-27-2013, 04:03 | posts: 23 | Location: Brazil

After some googling I found out that 7970s are shipping with 3 different voltages, namely 1.05, 1.112, 1.170 with the latter being the most common. According to MSI Afterburner, mine is at 1.05 voltage.

Am I right to think that since 1.170 volts is the most common, I might as well just up the voltage to that, overclock it to my heart's content, as if I never even tweaked the voltage on my card? Would it be safe to go even further, as if 1.170 was stock voltage?

Last edited by Dravonic; 02-27-2013 at 04:12.
   
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Deathchild
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Default 02-27-2013, 11:21 | posts: 2,162 | Location: Estonia

Yeah sure you can do that. Just keep an eye on your temps.
   
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yasamoka
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Videocard: 7970CF @ 1100/1375 H2O
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Default 02-27-2013, 12:18 | posts: 3,376 | Location: Lebanon

They come with different voltages because they are assured to be stable at the required stock clocks at those specific voltages. Each card is different and has difference tolerance to voltage.

The ones with high stock voltage are low ASIC cards. They respond really well to higher voltages and they OC well as you up the voltage. In return, they consume more power and run hotter.

The ones with low stock voltage are high ASIC cards. They overclock really well at stock voltages, but do not take too well to voltage increases. You'll find they hit a wall at a certain clock and voltage where no additional voltage can make the card stable. Low ASIC cards would generally overclock / overvolt beyond that wall PROVIDED YOU PROVIDE THEM WITH BETTER COOLING!

This means that, generally, on air, with moderate voltages, high ASIC cards OC better than low ASIC cards. This also means that, generally, on water, phase-change, and liquid Nitrogen, low ASIC cards OC better than high ASIC cards.


These voltages all fall within any 7970's voltage tolerance levels. All high ASIC cards I've seen easily take 1.17V, of course. But this isn't a general rule you can apply everywhere. This targets your question by providing an example:

Gigabyte 7950s recently came with a BIOS that ran the cards at 1000MHz stock clocks and 1.25V stock voltage. Gigabyte cards, however, seem to be low ASIC, so they can take those voltages and respond really well to them. You'll see them soar in OCing. There's even a thread about this very topic:
http://forums.guru3d.com/showthread.php?t=374287

However, high ASIC cards may not tolerate, or respond to, these voltages (1.25V). A friend's MSI 7950, 90% ASIC, reached 1100MHz @1.1V. Up the clock to 1125MHz, and not even 1.2V could make it stable. The highest stable OC, 1100MHz, was running at around 70C. The unstable OC, 1125MHz, was running at 86C! Of course, this is with stress testing, but I believe this is the way to OC your card, as with certain games, you'll realize your OC is unstable, and those games are, by themselves, as close to a stress test as you can get with a game.

This means that in general, with that voltage of 1175mV, yes, you can take your card there even if it has high ASIC although this is STILL considered overvolting (and comes with all the risks and tradeoffs of overvolting), as the card's stock voltage is still 1.0x V.

On the other hand, a low ASIC card that ships with a higher voltage may not be stable at stock clocks with a low voltage of 1.0x V that ships with high ASIC cards.

Two different cards, two different stock voltages, two different scenarios. Neither runs "stock" at the other's voltage.

Hope this answers your question.
   
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Dravonic
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Videocard: VisionTek 7970 3GB
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Default 02-27-2013, 17:20 | posts: 23 | Location: Brazil

Very helpful and thorough explanation, thanks a lot.

I've been playing with it and it would seem I'll hit at wall at 1125 or close to that. I'm still only at 1.112v, but that's only 75Hz more for a 0.062 increase in voltage (stable at 1050 stock voltage), and that's still unstable. Either way, I've already made a special edition card out of a standard one, I'm happy enough with that.

Last edited by Dravonic; 02-27-2013 at 17:24.
   
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