Second RX 480 not showing up. Can't CF! Bad GPU/Mobo?

[Hoeheyy]

Just built a new system with two RX 480s but the second one wont show up. In Wattman and 'Display Adapter' Only 1 GPU shows up with no CF option. It has showed up occasionally, maybe twice for an hour each time, in the last three days. Both cards spin up.

Things I have tried:
Reinstall/upgrade drivers
Fresh Windows Install
Disable XMP/OC/Turbo settings in Bios
Swapping cards between lanes.
Setting PCIe Lane 2 to primary display output

PC Components:
CPU: i7-6700 (Non-K)
MOBO: GA-Z170MX-Gaming 5
RAM: 16GB G.Skill 3000MHz DDR4 running @ 2133MHz
PSU: EVGA NEX-750B
GPU: 2 x RX 480 (Hopefully)

Thanks in advance.

 

[Shaun o]

If the two cards are not of the same brand or manufacturer Hoeheyy

What you need to do is look at both of the cards.
Find the specs of each card in relation to what clock speed the actual Gpu of each card is running at and also the memory speed and the frequency or speed each is running at.

Work out, if they differ.
What the lowest speed of card is in relation to the Gpu clock speed and the memory speed.

Place that card with a lower gpu, and memory clock speed in the first Pci-e card slot of your motherboard first of all.

Power the system up and check in The Ati driver control suite, and watman.
That the card has been detected and the stated clock speeds of that card are being reported correctly.

If ok, shut the system down.

And then place the other RX 480 card in the second Pci-e cased card slot of your motherboard.
It should force the second card if it has a higher Clock speed to sync to the speed of the card in the first Pci-e graphics card slot of your motherboard.

After that both cards should show all of the time in crossfire mode on your system ok Hoeheyy.

It is often due to a fact that in order for the cards to crossfire correctly both gpu`s of each card must be running at the same base clock speed, and memory speed in order to crossfire correctly.

They need to synchronise in both respects before picked up or displayed, set as a crossfire configuration.

 

[Hoeheyy]

If the two cards are not of the same brand or manufacturer Hoeheyy

What you need to do is look at both of the cards.
Find the specs of each card in relation to what clock speed the actual Gpu of each card is running at and also the memory speed and the frequency or speed each is running at.

Work out, if they differ.
What the lowest speed of card is in relation to the Gpu clock speed and the memory speed.

Place that card with a lower gpu, and memory clock speed in the first Pci-e card slot of your motherboard first of all.

Power the system up and check in The Ati driver control suite, and watman.
That the card has been detected and the stated clock speeds of that card are being reported correctly.

If ok, shut the system down.

And then place the other RX 480 card in the second Pci-e cased card slot of your motherboard.
It should force the second card if it has a higher Clock speed to sync to the speed of the card in the first Pci-e graphics card slot of your motherboard.

After that both cards should show all of the time in crossfire mode on your system ok Hoeheyy.

It is often due to a fact that in order for the cards to crossfire correctly both gpu`s of each card must be running at the same base clock speed, and memory speed in order to crossfire correctly.

They need to synchronise in both respects before picked up or displayed, set as a crossfire configuration.

One is a Powercolor and the other is a Gigabyte. They are both the 8GB reference cards. Does that make a difference?