Those are some pretty long cables but I dont think you will run into issues. If you are having them custom made just make sure they are sized accordingly. GTX 1080 cards peak out around 175 watts, this will be one of you biggest power leaches. 175/12= (12v rail is where all the juice is sucked, the rest is logic) is 14.5 amps. All of the charts are in larger segments with the lowest being 0-6 meters. In the 0-6 meter category its calls for #14 wire for 14 amps on the 12 V rail. Now lets take a look at different wire types and applications. More strands always = better. The application is considered open air so all that means better current rating. I've had this question asked of me a lot in RV forums but we are talking high current devices for 15 meter lengths. In my alter state I have a 40ft 5th wheel coach and go glamping in the summer months. I call it glamping because a coach that is nicer than some people houses with AC, cable TV, wide screen TV, Wifi, cushy bed, leather recliners etc hardly classifies as camping.
In the end you could run 500MCM and it wont matter as the old adage of a chain is only as strong as its weakest link and the pins in the connectors cannot be upgraded to a larger size. They are what they are.
I just happen to be an EE and my advice would be that I would not worry much. If it would make you feel better you will have to have these cables custom made so have them bump up the size of the wire by one, Another thing to avoid if you have high current concerns is to avoid bundling them too tightly Ohms law E=I/R so volts go down current goes up and vice versa. More current=more heat and bundling too tightly increases the heat. Also keep in mind that to meet specs for IEEE and UL they have to be able to withstand a 5% Vdrop or 11.4V on the 12V rail.
Your main ATX cable would be of no consequence. No high power consumption going on there. The other cable I would be looking at would be the 8 with second 4 pin optional cable that goes to you MOBO to power the CPU.
So in summation, Voltage goes down, current goes up...Current goes up, heat goes up. For shorter runs ie less than 6 meters its usually no concern. If you are custom ordering just have them bump up the wire size by one size on the Graphics and the 8 pin CPU cable and you will surely be covered no questions about it.
Here is a fairly decent chart for DC. It only covers 12 Volts and your 12V rail is where most of the high power draw comes from. Alternately you can use Ohms law to figure out the rest of the devices.
In the end you could run 500MCM and it wont matter as the old adage of a chain is only as strong as its weakest link and the pins in the connectors cannot be upgraded to a larger size. They are what they are.
I just happen to be an EE and my advice would be that I would not worry much. If it would make you feel better you will have to have these cables custom made so have them bump up the size of the wire by one, Another thing to avoid if you have high current concerns is to avoid bundling them too tightly Ohms law E=I/R so volts go down current goes up and vice versa. More current=more heat and bundling too tightly increases the heat. Also keep in mind that to meet specs for IEEE and UL they have to be able to withstand a 5% Vdrop or 11.4V on the 12V rail.
Your main ATX cable would be of no consequence. No high power consumption going on there. The other cable I would be looking at would be the 8 with second 4 pin optional cable that goes to you MOBO to power the CPU.
So in summation, Voltage goes down, current goes up...Current goes up, heat goes up. For shorter runs ie less than 6 meters its usually no concern. If you are custom ordering just have them bump up the wire size by one size on the Graphics and the 8 pin CPU cable and you will surely be covered no questions about it.
Here is a fairly decent chart for DC. It only covers 12 Volts and your 12V rail is where most of the high power draw comes from. Alternately you can use Ohms law to figure out the rest of the devices.
