iMac 2011 + HD5750 new EFI

[dimakot08]

Hello everyone. Sorry for the translator.
I have an iMac 2011 27" i7 and I needed to replace the video card in it. I purchased an HD 5750, it worked without any problems, but then the firmware update came and now the screen is black when turned on, but the iMac loads and works 100%.
I understand that the problem is that the new firmware efi imac 2011 27" does not support hd5750 graphics card.
I've been looking for information on how to make friends with them for a very long time, but I haven't found anything.
I flashed the flash bios (efi) of my imac on the programmer, because I know how to do it, but all the firmware was new and already without support for this card, which means I still have a black screen))
I see several solutions, but I don't have the necessary firmware and I'm asking for your help.
1 - flash the previous efi version of my iMac, but I don't have it on the Internet, at least I can't find it.
2 - Find a custom EFI for my iMac with support for this video card, but I didn't find one either.
3 - Change the ID of the video card so that the iMac sees it as if it is for example HD6790, but I do not find vbios for HD5750 MXM3 7

I know how to do all the above options, but I don't have firmware((

If you have other solutions, then I will be happy to listen to them!

Thanks!

 

[Nguyen Duc Hieu]

Another solution is to change the graphic card.
I installed a Quadro K1100m to an iMac 27" 2011 for a guy living near. He is happy with the new card now.
That card was taken off from my iMac 2009, when I upgraded to Quadro M4000m.
HD5750 is just problematic.

 

[dimakot08]

Другим решением является изменение видеокарты.
Я установил Quadro K1100m на iMac 27" 2011 для парня, живущего рядом. Теперь он доволен новой картой.
Эта карта была снята с моего iMac 2009 года, когда я обновился до Quadro M4000m.
HD5750 просто проблематично.

Да, конечно, вы можете купить еще одну видеокарту и даже другой iMac, но мне нужно сделать эту конфигурацию.

 

[Nguyen Duc Hieu]

Да, конечно, вы можете купить еще одну видеокарту и даже другой iMac, но мне нужно сделать эту конфигурацию.

It's totally not worth the effort.
I would just buy a Dell M5950, or an HP 6770m.
For the Dell M5950, you would just need to flash the modded vBIOS and turn it to a HD 6770m 1GB for iMac 2011.
For the HP 6770m, you'd need more work on soldering the EEPROM chip and resistors, but the solution has been documented and doable by skillfull persons like you. They are cheap, too.

 

[dimakot08]

Это совершенно не стоит усилий.
Я бы просто купил Dell M5950 или HP 6770m.
Для Dell M5950 вам просто нужно будет прошить модифицированный vBIOS и превратить его в HD 6770m 1 ГБ для iMac 2011.
Для HP 6770m вам потребуется больше работы по пайке чипа EEPROM и резисторов, но решение было задокументировано и выполнимо такими опытными людьми, как вы. Они тоже дешевы.

Мне непросто купить еще одну видеокарту. Пожалуйста, не предлагайте возможность покупки других видеокарт.

 

[protocold]

In the older macOS you can actually trigger a firmware update by placing a scap firmware file onto the EFI, run some command and it will trigger the flash on the reboot.

However apple now closed this loophole and wont let you use the same method to downgrade. [you can still use the same method to upgrade however]

I have been trying to research on how to do this. I extracted older firmware version from EFI update and for some mac they are .FD files which you can just write onto the SPI chip[without the correct serial/board # etc but it will work].

For the iMac 2011, it is .SCAP file [which I have attached it is one of the older version] BUT you cant just write onto the SPI chip. You can open it with UEFITool[It can see various section]. Maybe you can help figure out how to convert this into an image that can be written directly onto the chip?

I also came across https://github.com/theopolis/uefi-firmware-parser but it wont work with my old High Sierra... I need to find a different machine..