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MP 1,1-5,1 Rx480 can only boot into Windows, only in Pcie slot 2?

Hot_Freaks

Hot_Freaks

macrumors newbie
Original poster
Jun 17, 2020
6
1
I put a Visiontek Rx 480 8gb into my cMP 5,1 and the only way I can get it to output signal is to boot into an HDD with Windows 10 on it, and only if the card is in the second Pcie slot from the bottom.

If I try to boot into MacOS 10.13.6 it just keeps restarting with the chimes. I updated the firmware to MP51.0089.B00, and I installed a clean version of High Sierra on a thumbdrive to rule out anything with kexts on the old install on my SSD.

Pulled out all but the first two slots of RAM and tried SMC and triple PRAM resets with a USB keyboard. I'm powering the card with a splitter cable so it should be getting enough wattage

If I put my 5770 back in everything is fine.

I don't know what else to try. I'm inclined to just get a different card, but I'm confused as to why any card would behave this way. Figure if it was broken it just wouldn't run, rather than run seemingly fine but only in a very specific configuration.
 
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Nguyen Duc Hieu

Nguyen Duc Hieu

macrumors 68040
Jul 5, 2020
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Ho Chi Minh City, Vietnam
Hot_Freaks said:
I put a Visiontek Rx 480 8gb into my cMP 5,1 and the only way I can get it to output signal is to boot into an HDD with Windows 10 on it, and only if the card is in the second Pcie slot from the bottom.

If I try to boot into MacOS 10.13.6 it just keeps restarting with the chimes. I updated the firmware to MP51.0089.B00, and I installed a clean version of High Sierra on a thumbdrive to rule out anything with kexts on the old install on my SSD.

Pulled out all but the first two slots of RAM and tried SMC and triple PRAM resets with a USB keyboard. I'm powering the card with a splitter cable so it should be getting enough wattage

If I put my 5770 back in everything is fine.

I don't know what else to try. I'm inclined to just get a different card, but I'm confused as to why any card would behave this way. Figure if it was broken it just wouldn't run, rather than run seemingly fine but only in a very specific configuration.
Click to expand...

May upgrade the Mac OS to Mojave fix your problem?
Newer macOS tend to have better support for newer VGA cards.
 
tsialex

tsialex

Contributor
Jun 13, 2016
13,455
13,602
Hot_Freaks said:
I put a Visiontek Rx 480 8gb into my cMP 5,1 and the only way I can get it to output signal is to boot into an HDD with Windows 10 on it, and only if the card is in the second Pcie slot from the bottom.

If I try to boot into MacOS 10.13.6 it just keeps restarting with the chimes. I updated the firmware to MP51.0089.B00, and I installed a clean version of High Sierra on a thumbdrive to rule out anything with kexts on the old install on my SSD.

Pulled out all but the first two slots of RAM and tried SMC and triple PRAM resets with a USB keyboard. I'm powering the card with a splitter cable so it should be getting enough wattage

If I put my 5770 back in everything is fine.

I don't know what else to try. I'm inclined to just get a different card, but I'm confused as to why any card would behave this way. Figure if it was broken it just wouldn't run, rather than run seemingly fine but only in a very specific configuration.
Click to expand...
If it's the card below, you may damaged your backplane and/or your BootROM:

www.visiontek.com

Radeon RX 480 Overclocked 8GB GDDR5 Rear Blower 4M (3x DP, HDMI)

The VisionTek RX480 Overclocked Edition is everything a gaming card can and should be, and we have made it even more accessible than ever. You can play the latest eSports titles and the most popular AAA games or experience the next level of immersion w
www.visiontek.com www.visiontek.com

RX 480 with just one PCIe 6-pin input is known to damage the Mac Pro backplane, worst yet, you choose to install a card that is factory OC. One of symptoms of the damaged backplanes is to just boot Windows with the card.
 
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MIKX

MIKX

macrumors 68000
Dec 16, 2004
1,815
691
Japan
Why am I lately seeing many "new" members seemingly unaware why GPU makers put power sockets on their cards . . . and moreover . .also .. seemingly unaware of which power cables to use with them.

I can only presume that they dislike using Google for 20 ~ 30 seconds to find the solution, learn and avoid destroying their cMPS.
 
Hot_Freaks

Hot_Freaks

macrumors newbie
Original poster
Jun 17, 2020
6
1
I put my 5770 back in, tested it in both slots and everything works normally as far as I can tell. So my assumption is the card is broken/finicky and/or MacOs doesn’t like something about the ROM.

I’m already planning on a different card anyways, I‘m just not sure there’s other problems I’m missing with other variables like 10.13.6, bad RAM, processor configuration that’d give me headaches with an approved card.
 
MIKX

MIKX

macrumors 68000
Dec 16, 2004
1,815
691
Japan
If you are not using this GPU power cable then that is probably your problem.

TWO X MINI 6 PIN. TO ONE by 8 pin.

I assume that that you know www.amazon.com and can use Google.

TWO mini 6 pin to ONE 8 pin GPU cable.jpg
 
tsialex

tsialex

Contributor
Jun 13, 2016
13,455
13,602
Hot_Freaks said:
I put my 5770 back in, tested it in both slots and everything works normally as far as I can tell. So my assumption is the card is broken/finicky and/or MacOs doesn’t like something about the ROM.

I’m already planning on a different card anyways, I‘m just not sure there’s other problems I’m missing with other variables like 10.13.6, bad RAM, processor configuration that’d give me headaches with an approved card.
Click to expand...
You are seeing probably two problems caused by the overconsumption of the RX 480 with just one PCIe 6-pin input, PCIe slot damage and BootROM corruption (happens when the KernelPanic for the shutdown is saved on the NVRAM volume, inside the BootROM). Btw, I warned you about it before.

When you go back to your Apple HD 5770, a GPU with pre-boot configuration support (boot screens/boot picker/etc) and can be powered even with the PCIe slot damage, you have it working but it's common that newer cards don't work with the damaged slot.

With a MacEFI GPU or a PC GPU flashed to have pre-boot configuration support installed on your working x16 slot, you can force the boot disk selection and then boot macOS, but since your NVRAM is trashed, you can't boot macOS with a PC GPU and will boot Windows instead.

If you install another non-MacEFI GPU (like a 8-Pin Sapphire Pulse RX580) and still can only boot Windows, be aware that it's BootROM corruption caused by the over consumption on the PCIe slot by the RX 480. There were several users here on MacRumors with the same problem, I cleaned the BootROM SPI flash dumps and reconstructed the BootROM to a working state but the damage to the PCIe slot still continue. Some people had to replace the backplane to get two x16 working PCIe slots again.
 
Last edited:
tsialex

tsialex

Contributor
Jun 13, 2016
13,455
13,602
Hot_Freaks

Hot_Freaks

macrumors newbie
Original poster
Jun 17, 2020
6
1
Before I buy a new card is there any way to determine for sure whether I have damage? The diagnostic LEDs on the backplane are normal, AHT found no problems, and the voltages and temperatures look fine in istats menu.

I haven't run a stress test yet. Finding a torrent of ASD is about the only other thing I can think of, but that seems overkill.
 
tsialex

tsialex

Contributor
Jun 13, 2016
13,455
13,602
Hot_Freaks said:
Before I buy a new card is there any way to determine for sure whether I have damage? The diagnostic LEDs on the backplane are normal, AHT found no problems, and the voltages and temperatures look fine in istats menu.

I haven't run a stress test yet. Finding a torrent of ASD is about the only other thing I can think of, but that seems overkill.
Click to expand...
It's very difficult to identify a damaged backplane PCIe slot without knowing how to debug it with a scope.

You can infer damage with cards that are x16 starting to being identified as x8 or even x4, or PCIe v2.0 cards being identified as PCIe v1.0. To check this you need to install PCIUtils and run pcitree.sh. Other symptoms are frequent shutdowns when with load, Furmark will show this with easy.

ASD will help debugging since it can show if any sensors show erroneous values.
 
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