Re: Motherboard wont detect specific GPUs, but detects others, and GPUs work.

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A specific r9 380x. 39 390. and rx 580... When these 3 cards are inserted into the motherboard at all, it simply will not post.... Motherboard works fine with others rx 580s and rx 480s, and these cards work fine in other motherboards...
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Hello friend,
try using atikmdag-patcher, and you can see the information here POST
the app works on my rig, hope it helps your problem.

Oh dear, dude! the OP cant boot up, how could on earth he use pixel patcher

Look like I suggesting it too early, lol. But it may will be one of useful input beside other input. Power issue has mentioned above me. Failed POST has different causing. I just assume that's OP's rig have crashed in the driver. USB storage device or optical drive also can made failed POST process. But yes, the power issue is the most factor causing failed POST. Most people just do CMOS reset on this issue and solving it. Like the pic I posted here, I'm mixing R9 290 Reference with four RX. I'm using patcher with a one only readable card, then adding the other cards after. It works for me.