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7970 CFX Refusing to overclock

cadaveca

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#26
also strange how the lower rated card had trouble at the higher voltages, but explains the crashes despite its greater OC ability.
The lower-quality chip has higher leakage, and as such either it cannot handle the higher voltage because A: the leakage is too high, or B: the current draw at the higher voltages, because of that leakage, is hitting over-current limits.


So, why is ASIC quality important? Well, it's important in different ways, depending on what you want to do with the card...


For most users, the higher the ASIC quality, the better, and this will result in the most efficient chip at stock, but these same cards amy not clock very high.

For extreme users, they want low ASIC quality, as higher leakage tends to mean that when frozen and that leakage is dealt with, the card will perform better, and is less likely to coldbug, than a card with higher ASIC quality.


I try to monitor the data people are listing for ASIC quality, and i think that over time we'll be able to suss out which cards are best for which users, whether air, water, or extreme cooling methods are used, based oj specific ASIC quality ranges. Each user will want to look for cards within a pre-spoecfiied range to get the best 24/7 results.

Your own testing here confirms my own findings about silicon and leakage, and how those relate to clocking, so it's interesting to me that you seem to confirm the same thing. This is relatively a new addition to GPU-Z, but has been something I've personally been paying attention to for years. Many people have asked me why i think high-leakage parts are good ,as to an electrical engineer, this is not the case, as they look for the greatest EFFICIENCY, which may or may not relate to how the chip behaves at high frequencies and extreme cold.
 

Bishi

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#27
Thankyou for the informative explanation!

For what its worth I got them both to 1120 core which I'm relatively happy with, although I figure I could probably send one card back to VTX3D stating a crossfire compatibility problem (due to the different voltages) and get a second 1112mv card which may overclock better
 
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#28
Thankyou for the informative explanation!

For what its worth I got them both to 1120 core which I'm relatively happy with, although I figure I could probably send one card back to VTX3D stating a crossfire compatibility problem (due to the different voltages) and get a second 1112mv card which may overclock better

For chits N giggles are they both set to the same BIOS on the switch? You may have accidently changed the BIOS switch on one of them? The switch is sticking out the back of the card right next to the second Cross Fire plug, check it!