5,1 Mac Pro + Sapphire Nitro+ RX480 8Gb card - PCIe power question...

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5,1 Mac Pro + Sapphire Nitro+ RX480 8Gb card - PCIe power question...

I recently bought & installed a Sapphire Nitro+ RX480 8Gb GPU card.

I wanted to upgrade from the original 5770 for Mojave & some gaming - the 5770 was fine for the older games I played but obviously no Metal support/not Mojave compatible.

After I bought it, I came across conflicting information about the Sapphire RX480 card & the power draw

from the PCIe slot.

I also was unable to find exact information about power requirement, even from the Sapphire site or promo material.

This is my card below:

On another online group/forum I was originally told by one member that the card would draw too much power & burn out the back plane.

Then another member said version of RX480 that I have (single 8pin power version) was fine & other versions of the RX480 would draw more power....

Not being able to get an exact answer online, I wanted to know if there was a way/app to find out how much power the 480 was pulling out of the PCIe slot?

Im using the dual mini 6pin to single 8pin connector to get 150w + whatever it's drawing from the PCIe slot.

Thanks in advance!

Mac Pro

Posted on Jul 26, 2020 11:26 PM

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Answer 1

Top-ranking reply

Grant Bennet-Alder

Level 10

133,231 points

Jul 30, 2020 7:18 PM in response to DJstylus

You are not confused. That is exactly "by the book".

For less than the heaviest of Video editing, Readers have found they can "get away with" under powering a little bit, but not grossly. So a card with a six and an eight run by two sixes may technically be under powered, but you can sometimes get away with that setup.

5 watts over? that will work.

55 watts over? you may have problems.

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Answer 2

Jul 27, 2020 7:16 AM in response to DJstylus

For talking purposes, we think of the slot itself as supplying 75 Watts.

A six pin aux cable supplies 75 Watts

An 8-in aux cable could theoretically supply 150 Watts, but in a Mac Pro, that is coming from a socket on the mainboard intended for 75 Watts. If you need more than 75 Watts out off it, you are more likely to have this work if you use an aux cord that has eight full-length conductors. A cord with short jumpers may not be able to carry near the 150 Watts you need.

The penalty for undersupplying power is that when you push the card really hard, it may over-draw the Mac power supply, which causes an emergency power-down to prevent damage.

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Answer 3

DJstylus Author

Level 1

15 points

Jul 30, 2020 6:41 PM in response to Grant Bennet-Alder

Thanks Grant but I'm confused - Im using a dual mini 6pin to 8pin connector which means it's pulling 75w out of each mini 6pin outlet on the main board, therefore 150w?

Then a further 75w from the main board?

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