MP 1,1-5,1 MacPro 5.1 - Won't load OS (stuck on loading screen) - GPU issue

[overshoot]

Hello,

I've purchased a faulty MVC GTX 780 GPU for my MacPro 5.1 thinking I could fix the short circuit.
To my surprise, the MacPro would start up, show a boot screen and try to load the OS. I thought it was not even dead until it got stuck on the loading bar...

I can confirm the GPU is the issue as swapping it with a known good one, the OS will load (HS or Mojave)

Is there a way the Bios could be the issue or it has to be a faulty GPU chip like on the 2011 MBP?
Thanks!

 

[DearthnVader]

Is there a way the Bios could be the issue or it has to be a faulty GPU chip like on the 2011 MBP?

Likely a faulty GPU, but I have seen legacy VBios on a R280 cause the same issue.

The macOS graphics drivers for both AMD and nVidia use the legacy Vbios to setup the drivers. If it finds something there it doesn't like, booting will freeze like this.

Booting in Verbose mode will often tell you more.

In the case of my R280, flashing a "better supported" video bios to the card fixed the issue, but I was able to confirm the card worked as expected in a PC before I flashed, so I knew it wasn't a hardware issue with the GFX card.

Like I say, likely you just have a bad graphics card, and MVC cards are sort of a blackbox, tho, I think they preserve the legacy video bios, so you should be able to test the card in a PC, just be sure you have CSM enabled for legacy vbios support on any modern PC.

 

[overshoot]

Thanks! I'll try that first.

 

[overshoot]

Well it turns out I got a message before loading Windows saying to plug the PCIe cables. So disconnecting those cables didn't make any difference. I then disassembled the card hoping to find a blown fuse on the power lines but I ended getting a blown capacitor and 2 ripped of transistors. That's good news cause the GPU chip itself might still be fine. I have soldering skills so I'll order those parts and replace them and see if it works.

 

[MIKX]

The GTX 780 MUST have power to the 8 pin & 6 pin sockets.

From the Mac Pro pro's motherboard = 2 x Mini 6 pin to 1 x 8 pin to GPU

From TWO empty SATA ports = 2 X SATA to 1 x 6 pin to GPU.

 

[Snow Tiger]

Well it turns out I got a message before loading Windows saying to plug the PCIe cables. So disconnecting those cables didn't make any difference. I then disassembled the card hoping to find a blown fuse on the power lines but I ended getting a blown capacitor and 2 ripped of transistors. That's good news cause the GPU chip itself might still be fine. I have soldering skills so I'll order those parts and replace them and see if it works.

It is a bad idea to power up a GPU without all of its PCIe power boosters connected and working . The GPU will attempt to operate with whatever power sources it is connected to ( in this case , the PCIe slot of your logic board ) . The draw will exceed tolerances and you could burn out the slot . This happened to a client of mine who performed a self install in a cMP with an AMD Titan , which was improperly powered . The card survived , but she fried PCIe Slot 1 of her cMP .

 

[overshoot]

Good to know. Thanks!

 

[Itconnects]

Never had this issue before but after a long time of not turning it on I’m stuck here for about 20 minutes before reaching the log in screen. I eventually log in, but the process seems suspect. I don’t think it’s a GPU issue though.

Mac Pro 5,1
Mojave

 

[Itconnects]

Never had this issue before but after a long time of not turning it on I’m stuck here for about 20 minutes before reaching the log in screen. I eventually log in, but the process seems suspect. I don’t think it’s a GPU issue though.

Mac Pro 5,1
Mojave

Solved: After a couple restarts, everything loads normally