My point is that the GPU fans cool the top of the card, but not the back.
GDDR5 temps are not easy to measure and this type is only rated to work up to 70℃.
There seems to be issues with some Gigabyte Windforce GTX780Ti versions, but just when crunching here. We think its related to the GDDR5, it's voltage/the VRM and we've identified that it uses H5GQ2H24AFR-R2C (at least in Zoltan's case) and this requires 1.6V (rather than 1.5V for some 7GHz modules or 1.35V for some 6GHz GDDR modules). Obviously 1.6V generates more heat than 1.5V...
So while there might be a design fault, there is nothing we can do to fix that, but we can try to treat the symptoms.

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Thank you for your message !

I am currently tryng to run short WU's

Have decreased the MEM CLOCQ by 300 Mhz

The volatge shown on EVGA Precision X is 1.2 for card 0 and 1.175 for card 1

Have added extra external fans, (= 4 external fans) in order to cool the back of the cards +
have now the PSU outside the case (it's a real mess ;) )

Will see if it works.

Thank You

Philippe

Would GPU WaterCooling be the ideal solution ?

Or better to change for 970/980 ?

Thank You

EDIT : It seems that today not only 780Ti have problems :/

EDIT 2 : I give up. All WU's crashing.

Hello !

Currently running other tests.

MB = ASUS Z87 Pro / PSU CORSAIR RM 1000

When GPUGRID runs on both GPU, the GPU Load =

94 % on card 0

65 % on card 1

?

=> WU on card 0 crashes first, and after a few seconds only.

This afternoon, I will try to run GPUGRID on card 1 (looks to be slow but TBC)
while running Collatz on card 0 (GPU Load = 99 %)

NB : The cards are 100 % stable running Collatz with high temp + GPU Load 99 %, even when both GPU @ work.


Do you think that GPU Watercooling might help ?

NB2 : 2 small external fans directed on the GPU's back ...

Thank You

I do not think that water cooling is the answer as all tasks are failing on your card.
If cooling the back failed then I can only suggest reducing the GDDR5 down to 3000MHz or less.
I suggest you get rid of the GTX780Ti as your Gigabyte Windforce doesn't work well here.
A GTX970 should be a good card when the apps work well with the GTX900 range.

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Thank you for your message.

However, when I read all posts related to errors with the same code
"simulation as become unstable", on different types of cards,
I am wondering if buying 970 or 980 will really "solve the problem" ...


EDIT : Bought 2 * GTX970 Gigabyte Gaming G1 WindForce 4Go.

Hope it will work ;)