MP 1,1-5,1 Upgrade GPU on flashed cMP 4.1 to 5.1 without Bootscreen on Open Core - Big Sur

[Omnath]

Dear community,

Some time ago I bought a fully upgraded and flashed cMP 4.1 to 5.1 with the best possible specs (afaik) using an AMD Radeon RX 580 8 GB Pulse. Everything works perfectly smooth with Open core from Martin LO but with Megapixel AI and Denoise AI the computer shuts down immediatly. Found out the GPU has not enough power.

I'd like to go for a GTX 1070 FE, GTX 1070 Ti FE or GTX 1080 FE since they work with the mainboard power. Only thing I'm nor sure about is the "without bootscreen" thing and if there are any compromises besides that if I don't flash the card? I'm in Europe and MVC would be really expensive.

Right know I hear the Apple start up sound and then can choose between Windows and Big-Sur (Windows is standard and I don't know how to change that). I don't need to see that because I know the timing already. Does everything work after that with one of those cards? What if something needs to be fixed with Open Core? Do I only get blank screens then?

Thanks for helping me out and sorry for my noobish questions.

 

[tsialex]

Seems you are not thinking this right, you will downgrade to High Sierra to install a Pascal NVIDIA GPU?

 

[Omnath]

Thank you very much! I really didn't see that... So my only option without power mods would be the "AMD Radeon RX 480 8GB" since I need 2 Display Ports. Is it the same compatibility with the 580?

I'm unsure because of this:

AMD Radeon RX 580 8 GB
Other: occupies 2 slots, no Boot Screen. There are much models with different frequencies. That card is recommended by Apple for Mojave (SAPPHIRE Radeon PULSE RX 580 8 ГБ GDDR5).
Unflashed (PC version): works out of the box. Can be flashed by MVC.

AMD Radeon RX 480 8GB
Unflashed (PC version): works without Boot Screen.

Is there a difference or does it mean it's actually the same compatibility?
Thanks again

 

[tsialex]

Thank you very much! I really didn't see that... So my only option without power mods would be the "AMD Radeon RX 480 8GB" since I need 2 Display Ports. Is it the same compatibility with the 580?

I'm unsure because of this:

AMD Radeon RX 580 8 GB
Other: occupies 2 slots, no Boot Screen. There are much models with different frequencies. That card is recommended by Apple for Mojave (SAPPHIRE Radeon PULSE RX 580 8 ГБ GDDR5).
Unflashed (PC version): works out of the box. Can be flashed by MVC.

AMD Radeon RX 480 8GB
Unflashed (PC version): works without Boot Screen.

Is there a difference or does it mean it's actually the same compatibility?
Thanks again

RX 480 is known to damage MacPro PCIe slots, since most of the cards draw more than 75W from the PCIe slot - a big no-no with a Mac Pro. It's extremely difficult to find a RX 480 with a 8-pin power connector. People that have a RX-480 and will tell that works are the people that don't use it full-throttle or don't know that the backplane is already damaged.

Buy a eVGA PowerLink and test if your RX 580 works correctly after that, you will need two mini-PCIe 6-pin cables to feed the PowerLink.

Maybe a RX5700, non XT, would be a better option for you, performance and power draw wise, but it's only supported by macOS after Catalina.

 

[Omnath]

Thanks again!

I already have two cables (6 pin and 8 pin) connected to my RX 580 which come from the mainboard and look like small 6 pins to me so I guess its the mini-PCIe 6-pin you mentioned. Would the eVGA PowerLink offer any benefits over my current cables?

A RX5700 would be costly and I don't need that much performance actually. I'm quite happy with my RX580 performance wise. But if I decide to upgrade: is the RX5700 supported the same way like the RX580? It's not mentioned in the compatibility list sadly :/

 

[tsialex]

Thanks again!

I already have two cables (6 pin and 8 pin) connected to my RX 580 which come from the mainboard and look like small 6 pins to me so I guess its the mini-PCIe 6-pin you mentioned. Would the eVGA PowerLink offer any benefits over my current cables?

Yes, PowerLink balances the load between the two PCIe AUX connectors, eliminating SMC shutdowns where one of the AUX connectors is drawing much more than the other, probably what is happening to you right now.

Also, spikes are attenuated with the internal capacitor.

A RX5700 would be costly and I don't need that much performance actually. I'm quite happy with my RX580 performance wise. But if I decide to upgrade: is the RX5700 supported the same way like the RX580?

No, supported by Catalina/BigSur/Monterey only. Power wise is more efficient than the RX 580.

It's not mentioned in the compatibility list sadly :/

Because it's up to Mojave.

 

[Matty_TypeR]

Thanks again!

I already have two cables (6 pin and 8 pin) connected to my RX 580 which come from the mainboard and look like small 6 pins to me so I guess its the mini-PCIe 6-pin you mentioned. Would the eVGA PowerLink offer any benefits over my current cables?

A RX5700 would be costly and I don't need that much performance actually. I'm quite happy with my RX580 performance wise. But if I decide to upgrade: is the RX5700 supported the same way like the RX580? It's not mentioned in the compatibility list sadly :/

The RX580 is fine, but the RX 580 with 1 x 8pin and 1 x 6 pin are not equal on power draw. the EVGA power link will even out the power draw on the 580 you have. you can carry out the Pixlas mod so you can use power direct from the PSU.

Its not worth burning the power tracks to the dual mini 6 pin mounts on the logic board with a mini 6 pin to 8 pin cable. but like everything else the logic boards are 10 years old now and although good if you push past the 225w with power spikes you run the risk of damaging the logic board which you cant even buy new.

mini Pcie 75w x 2 = 150w + 75w max pcie slot for gfx card = 225w all together. Pixlas mod is best to handle the power draw.

 

[tsialex]

Btw, you are using a Sapphire Pulse RX 580 with just one mini-PCIe 6-pin to 8-pin? Why?

It's a Sapphire Pulse or Nitro+?

 

[Omnath]

Yes, PowerLink balances the load between the two PCIe AUX connectors, eliminating SMC shutdowns where one of the AUX connectors is drawing much more than the other, probably what is happening to you right now.

No, supported by Catalina/BigSur/Monterey only. Power wise is more efficient than the RX 580.

Since I'm running on Big Sur and soon Monterey I guess the support below is not of interested to me. Is the RX6600 or RX6600 XT an option? On the Mac Pro it says Radeon Pro W6600X MPX Modul is supported since OS 12.3 -> does that mean the RX6600 is natively supported in the cMP with OS 12.3 as well or would that be too easy?
Is it important from which manufacturer they are produced and if they are OC? On the used market I mainly can find 3rd party GPUs.

Btw, you are using a Sapphire Pulse RX 580 with just one mini-PCIe 6-pin to 8-pin? Why?

I am using a Sapphire Pulse RX580. I have 2 cables installed. 1 from 6 to 6 pin and another from 6 to 8 pin. I bought it this way from a guy who upgrades old cMPs.

Its not worth burning the power tracks to the dual mini 6 pin mounts on the logic board with a mini 6 pin to 8 pin cable. but like everything else the logic boards are 10 years old now and although good if you push past the 225w with power spikes you run the risk of damaging the logic board which you cant even buy new.

mini Pcie 75w x 2 = 150w + 75w max pcie slot for gfx card = 225w all together. Pixlas mod is best to handle the power draw.

I was thinking about the Pixlas Mod as well but thought it was risky and better to use the logic board power from the two cables. I was mistaken I guess. Will probably do this if it keeps my computer healthy

Thanks to both of you big times!