I had some time today, so I put my cards in to identical situation and tested the max clockspeeds with watercooling (very simple loop and small radiator)
The interesting thing is, that when you push your card to the maximum clock and you do not use fixed voltage, cards start to act more unpredictable. (quite obvious)
Well, that is only partially true. There is thermal shutdown mechanism still active on these cards, even all other protection is shutted off with modifications and software.
The cards which can scale with voltage are in the top of the chart and the cards which have thermal issues are on the bottom. (see reference / lightning)
Now it is easy to pick up 4 cards to my next 4-way SLI overclocking session

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