I've got 2 graphics cards, a gtx 680 2gb and a gtx 580 3gb.. which one would be faster and is it even possible to run the gtx 580 as it uses a 8+6 pin plug .
well for games i think the 680 is faster for cuda/opencl the 580 may be faster but i dont know for shore.
the nvidia topic i linked to says more on the subject https://forums.macrumors.com/thread...out-nvidia-pc-non-efi-graphics-cards.1440150/
post 5
Note that while cards like the GTX 480 and GTX 580 technically work, they have a TDP of 245-250W which is above what the Mac Pro can officially support (225W). If you want to use these cards, you'll probably have to drive them with an external power supply. In general, a card like the GTX 570 would be a better choice, since it has a TDP of 219W.
&
post 18 https://forums.macrumors.com/thread...l-efi-boot-screens-etc-gtx570-gtx580.1360927/
&
post 21 - Why is the GTX 570 better than the GTX 680 for CUDA and OpenCL?
Many people get confused by the different core counts for the Fermi and Kepler generation cards. The architetural differences are discussed in detail in the AnandTech review of the GTX 680, and it's worth reading the whole article if you'd like to understand the differences.
i assume if the 580 is any faster (depending on workloads) the 'joy' of using an external power supply and power-use/heat/nose the point is almost lost and id just pick up a RX560/580 instead or stick with the 680.