iM 4,1-14,4 2011 iMac Graphics Card Upgrade

[piwikiwi]

Hi everyone,

I think I have collected everything i need to install a flashed W5170M in my 2010 iMac 11.2. I am unable to find anyone locally to perform the install so I'm giving it a shot.

In Ausdauersportler's Nov 3, 2021 post he mentions that OCLP from version 0.3.2 will be able to autodetect the new GPU and create a working Opencore installer.

https://forums.macrumors.com/threads/2011-imac-graphics-card-upgrade.1596614/page-668?post=30564216#post-30564216

Does this mean that if the mac is running Sonoma and OCLP 2.2 that the mac can be disassembled without making any software changes prior to installing the new card?

I noticed that if I set the MXM GPU to AMD GCN and attempt to build Opencore (which is what the GPU seller in China suggests) before installing the new GPU that the installer is unable to build Opencore (it starts and then delivers an “Unable” error message)

FirePro W5170M 2GB R9 M375 216-0866036 Video Graphics Card 109-C93157-00A 0K422C For Dell Precision 7510 7710 iMac A1311 A1312 - AliExpress 7

Smarter Shopping, Better Living! Aliexpress.com

www.aliexpress.com

Thanks very much for all the advice so far and any new advice related to my question today


Paul

 

[countryhick]

Hello again!


Did a whole lot of trying out to get my WX4130 to work again. New USB stick for both GRML and OCLP. Was able to get GRML to boot and SSH'd in. Confirmed card to be showing the correct vbios build after initially having "SSID mismatch" on the first flash. "SSID mismatch" went away after force flashing the vbios. Backlight comes on at boot and it displays the boot picker as well as GRML. Check pic.

I then tried several OCLP installs to get somewhere at least. Wiped the SSD each time:

- Ventura: Install seemed to run ok but black screen.
- Sonoma: Install seemed to run ok but black screen.
- Sequoia: Install didn't run until black screen.

For both Ventura and Sonoma I ended up with a black screen with backlight on after the expected several reboots from install just like last time. During install for both versions I could see progress bars and normal imaging. I could also see verbose output until black screen. I suppose this is when the install switches over to internal video drivers. Then something breaks.

Sequoia didn't install cleanly and I didn't pursue further as Sonoma was my target install due to stability.

For both installs with the black screen I could see a running system with an active IP in my router's dhcp table. Tried to SSH into it but was denied as expected as SSH access wasn't yet configured.

For both installs with the black screen nothing was shown on an external display. External display went to auto-off.

I'm out of ideas as I have tried every possible variation. Any comments are welcome.View attachment 2483373

Gday,

Sounds like a similar experience I had with one of my 4130's.... My Post
Long story short.. It was faulty

 

[howardc64]

Hi everyone,

I think I have collected everything i need to install a flashed W5170M in my 2010 iMac 11.2. I am unable to find anyone locally to perform the install so I'm giving it a shot.

In Ausdauersportler's Nov 3, 2021 post he mentions that OCLP from version 0.3.2 will be able to autodetect the new GPU and create a working Opencore installer.

In my experience, OCLP will auto detect iMac version + GPU in most cases (doesn't do wx3200 correctly which I've documented in the website in signature link) when building and installing OC and build USB installer.

However, as good practice, should always set the proper Model ID and GPU setting. 11,2 and AMD GOP Injection + AMD GCN.

https://forums.macrumors.com/threads/2011-imac-graphics-card-upgrade.1596614/page-668?post=30564216#post-30564216

Does this mean that if the mac is running Sonoma and OCLP 2.2 that the mac can be disassembled without making any software changes prior to installing the new card?

There are multiple ways to install OCLP. Simplest way for newbies is just

• build correct USB installer
• change GPU, wipe boot drive, boot installer and install

You are probably asking about the more "advanced" way

• Install OCLP macOS before making hardware changes (SSD is desirable to install and run much faster)
• After OCLP properly installed (OC->EFI, macOS patched (latest OCLP installer complete the patch before setting up iMac) and macOS setup. Can 1) build OC for W5170M and install into EFI 2) revert the root patch. Then shutdown
• Change GPU, boot up, apply AMD GOP Injection + AMD GCN root patch

I noticed that if I set the MXM GPU to AMD GCN and attempt to build Opencore (which is what the GPU seller in China suggests) before installing the new GPU that the installer is unable to build Opencore (it starts and then delivers an “Unable” error message)

Not sure why, I run OCLP on my fastest macs not running OCLP to build installers. Make sure set model ID + GPU settings correctly per above.

 

[internetzel]

In my experience, OCLP will auto detect iMac version + GPU in most cases (doesn't do wx3200 correctly which I've documented in the website in signature link) when building and installing OC and build USB installer.

However, as good practice, should always set the proper Model ID and GPU setting. 11,2 and AMD GOP Injection + AMD GCN.



There are multiple ways to install OCLP. Simplest way for newbies is just

• build correct USB installer
• change GPU, wipe boot drive, boot installer and install

You are probably asking about the more "advanced" way

• Install OCLP macOS before making hardware changes (SSD is desirable to install and run much faster)
• After OCLP properly installed (OC->EFI, macOS patched (latest OCLP installer complete the patch before setting up iMac) and macOS setup. Can 1) build OC for W5170M and install into EFI 2) revert the root patch. Then shutdown
• Change GPU, boot up, apply AMD GOP Injection + AMD GCN root patch

Not sure why, I run OCLP on my fastest macs not running OCLP to build installers. Make sure set model ID + GPU settings correctly per above.

If you try disabling AMD GOP injection on your machines you will notice that it's almost never needed - and even less for VBIOSes linked here, since they all have GOP drivers included.

 

[piwikiwi]

Thanks guys,

unfortunately I'm not sure that we're talking about the same thing, although it's probably just my lack of understanding.

My specific question is:

can I just open up my iMac 11.2 (running perfectly, Sonoma and OCLP 2.2.0 installed and patched on internal SSD), drop in the W5170M (with new thermal paste and pads and maybe a shim), and then bootup the mac and check the OCLP settings and repatch?

Or: do I need to change the settings in OCLP to "enable AMD GOP injection" and "Graphics Override: AMD GCN" and then rebuild and install OpenCore AND THEN drop in the W5170M? (thanks howardc64 and internetzel: setting the model ID actually took away the error message that I previously had 👍)

Or: something else?

Thank you very much for whatever advice you might have 🙏,

Paul


Images:

 

[howardc64]

Or: do I need to change the settings in OCLP to "enable AMD GOP injection" and "Graphics Override: AMD GCN" and then rebuild and install OpenCore AND THEN drop in the W5170M? (thanks howardc64 and internetzel: setting the model ID actually took away the error message that I previously had 👍)

Do this (If don't update EFI OC to W5170M before changing GPU, mac won't boot after shutdown) AND the following before shutdown and change GPU

• revert root patch (remove drivers for the OEM GPU)
• close all applications and turn off any auto launched apps during login (see below)
• have to do ALL these 3 steps before shutdown to change GPU. If skip some steps, likely encounter problems

After W5170M install and boot up again, it will run slow with visual anomolies (no new GPU drivers installed) until root patch + reboot.

This is a more advanced installation method as I explained in prior reply. (OCLP macOS already installed on prior GPU followed by changing the GPU without wiping the drive) It is more difficult to explain and understand due to the multiple manual steps required.

For newbies, usually its far easier to make an USB installer and wiping the drive (wiping drive has its own complexities depending on what EFI is on the drive so best just remove drive, wipe entire drive using another mac, and reinstall) to avoid having to do more advanced method requiring 3 manual steps and potentially making mistakes.

Not sure why you need to set model ID if OCLP is running on iMac 11,2. It should just auto detect to this Model ID.

Or: something else?

Thank you very much for whatever advice you might have 🙏,

Paul


Images:

View attachment 2485799


View attachment 2485800

These settings are correct.

 

[howardc64]

If you try disabling AMD GOP injection on your machines you will notice that it's almost never needed - and even less for VBIOSes linked here, since they all have GOP drivers included.

Thanks, I'll try on future builds

 

[piwikiwi]

@howardc64

I’m really sorry for asking a question that you’ve pretty much already answered in detail but punctuation and quotation marks are messing with my head

Prior to cracking the case the 3 steps are:

1) change the settings in OCLP to "enable AMD GOP injection" and "Graphics Override: AMD GCN" and then rebuild and install OpenCore
2) revert root patch (remove drivers for the OEM GPU)
3) close all applications and turn off any auto launched apps during login (see below)


Correct?

No guarantees of course, just trying to minimize errors 😃

Thanks again (and again),

Paul

 

[howardc64]

@howardc64

I’m really sorry for asking a question that you’ve pretty much already answered in detail but punctuation and quotation marks are messing with my head

Prior to cracking the case the 3 steps are:

1) change the settings in OCLP to "enable AMD GOP injection" and "Graphics Override: AMD GCN" and then rebuild and install OpenCore
2) revert root patch (remove drivers for the OEM GPU)
3) close all applications and turn off any auto launched apps during login (see below)


Correct?

Correct.

After GPU change and boot up. Confirm AMD GOP Injection + AMD GCN still set (latest OCLP remembers last setting) and root patch then reboot.

No guarantees of course, just trying to minimize errors 😃

Thanks again (and again),

Paul

 

[piwikiwi]

Thanks 😃

 

[Pacific1972]

spring is coming !

... if reading this thread, looking at the last activities to OCLP and ebay prices
of A1312 spare parts & compatible 3rd party GPUs to 2009-2011 iMacs - I smell
light breeze of uplifting inspiration !

I have both old and new Apple hardware in use, but like the possibilities
of modifying an iMac A1312 with different GPU, Intel CPU, SSD and RAM...

The opportunities for using 32Bit High Sierra (STEAM & more) together with another
newer 64Bit macOS + Parallels (Update -> WIN11 - setup /product server) and Linux
on a bigger SSD means: you can do everything with except perhaps the newest games !

Early Intel Mac

👏 Look at this Desktop Setup from macrumors-user eyoungren - that is 😇 pure religion !

​

I think the future focus of the “upcycled iMac” A1311 and A1312 will not only be on the OCLP
experimental use of new 64Bit macOS operating systems, but also on the explicit use of
retro 32Bit macOS High Sierra + WIN11 + Linux together (necessity of large SSD and a lot
of RAM, should all operating systems be used) !

Hopefully everyone can get enough spare-parts / cooling parts
to let the "Early-intel-Macs" run ! The design is 👽 "Alien" !

 

[snackbar]

There are a lot of variables, which heat sink you have and which GPU card. My wx4130 experiences were all 12,2 2 pipe heat sinks. 3 pipe heat sinks have different fit. Don't know about your 12,1 + wx4130.

I have 0.3-1.5mm shims and just choose the correct thickness to make sure all inductors don't touch any part of the heat sink by visual inspection. It might be slightly thicker than necessary but easy to do. Of course this require to have a whole range of shims in hand.

I've never encountered inductor touching heat sink myself. But from reading this thread, it will cause a short and iMac won't boot? Not sure without personal experience.

Alright, after finding the time I added a 0.5mm 15x15mm shim with K4-Pro on both the GPU die and the shim's topside. K5Pro for the VRAM. 21.5" 2011 with the two lane heatsink.

No change. OCLP Sonoma install goes straight to black screen with backlight on. After some time, the backlight turns off and doesn't come back on again. Looking at some mentions here it seems the card is dead. Now going to try to return the card via Aliexpress... to China.

Anyone know of a reliable source for a WX4130 in Europe? Or any hot tip for a GPU to bring the system to Sonoma?

 

[howardc64]

Alright, after finding the time I added a 0.5mm 15x15mm shim with K4-Pro on both the GPU die and the shim's topside. K5Pro for the VRAM. 21.5" 2011 with the two lane heatsink.

No change. OCLP Sonoma install goes straight to black screen with backlight on. After some time, the backlight turns off and doesn't come back on again. Looking at some mentions here it seems the card is dead. Now going to try to return the card via Aliexpress... to China.

Anyone know of a reliable source for a WX4130 in Europe? Or any hot tip for a GPU to bring the system to Sonoma?

GCN4 is becoming more rare+costly on (US)ebay

iMac 12,x (4 core+AVX) + Kepler + OCLP 2.2.0 runs reasonably well on Sequoia (I presume Sonoma too) if accept temporary initial setup slowness from shader compiler tasks. Post #22234 has more info.

 

[Yomaho]

Sierra and High Sierra Package Installer

( iMac 2009-2011 AGC, FakeSCM, Lilu, WhateverGreen, AppleBacklightFixup installer)

(not compatible with OCLP or Catalina Loader/OpenCore, replaced in functionality by OCLP)
​

Attached you will find the a kernel extension package installer currently working on Sierra 10.12 and later. SIP needs to be disabled. Boot into recovery, start Terminal app, enter csrutil disable and reboot directly into your macOS and install the package.

It will patch the current installed AppleGraphicsControl (AGC) as described in this post addressing the black screen issue and install the AppleBacklightFixup needed for ++ type Nvidia cards side by side with the @vit9696 Lilu and Whatevergreen. As an option you can have the FakeSMC extensions get installed.

The NVIDIA ++ cards are this running with a BIOS from @nikey22 and marked in the table on post #1 as type ++.

After starting the Apple package installer (double click) you can choose the destination and select the packages to be installed according to your wishes. For this reason I separated the complete sets in several subsets. You can use the installer to patch AGC (this will be done in any case), and install addionally BacklightFixup, FakeSMC, and WhateverGreen/Lilu. You have to select at least one kernel extension to be installed. Only the FakeSMC is really optional.

FakesSMC will be needed b the HW Monitor app to provide full details on all sensors available on your system.

What will this package installer do:

1. Patching AppleGraphicsControl AGC (all iMacs, Nvidia card users, only)
2. Nvidia BacklightFixup (all iMacs, only NVIDIA ++ GPU)
3. FakeSMC Package (all iMacs, all graphics cards)
4. vit9696 WhateverGreen and Lilu (not compatible with OCLP and Catalina Loader)

Supported hardware:

iMac 11,x (Late 2009 and Mid 2010) with NVIDIA Kepler GPU
iMac 12,x (Mid 2011) with NVIDIA Kepler GPU


Supported MacOS:
macOS Sierra 10.12.1, High Sierra, only!

on iMac11,x please use OCLP
on iMac12,2 please user other packages with Mojave/Catalina


Recipe:

Disable SIP, download package, double click, enter password if asked for, select disk and the extensions to be installed, finish installation and reboot.

You may select only a single of the packages below! The AGC patch will be applied in any case.

View attachment 1666152


Attached you will find some selections screen shots. You can use the installer to select a single package only.

Have fun and please report back!

Notes:
12/07/2020: Late Nikolaus gift, new package installer and deinstall package

10/20/2022: You may use the AppleGraphicsControl AGC patch only using AMD GCN4 cards, too. Deselect all three other options (Nvidia, FakeSMC, Lilu/WhateverGreen) to avoid the black screen issue on High Sierra!

Looks great but sadly doesn't work under High Sierra.
It says :
"Failure
This programm works for macOS Mojave 10.14.1 and bove. Use on macOS Mojave 10.14 xxx and newer until macOS Catalina 10.15.7"
How can I use it on High Sierra please ?

 

[Pacific1972]

Looks great but sadly doesn't work under High Sierra.
It says :
"Failure
This programm works for macOS Mojave 10.14.1 and bove. Use on macOS Mojave 10.14 xxx and newer until macOS Catalina 10.15.7"
How can I use it on High Sierra please ?

Hello, you can use KEXTDrop App + added KEXT files to save this into S/L/E (System/Library/Extensions).
I hope, that are the right ones for High Sierra, additional Mojave & Catalina are zipped on my SSD.
If you can use that for AMD/ATI I don't know, that are I think only for NVIDIA Quadro + NVIDIA GTX 😊

I've read some of your previous posts to understand what your problem is...
Also you want to have WIN, 64Bit Big Sur and 32Bit High Sierra on one or
more HDD / SSD ?

It means:

- OCLP + Boot Loader is only the solution for 64Bit BigSur and unsupported OS (not Mojave / Catalina)
- 32Bit High Sierra is native, so you need only the KEXT Files -> save to S/L/E
- WIN (Legacy Mode installation - standalone) is native (no need of OCLP) !

Make 3x partitions, install High Sierra first (you only need the KEXT files -> Black screen patch),
then install WIN (Legacy mode - native) without OCLP, but - of course - all downloadable drivers
for the hardware, third you can install OCLP-patched 64Bit Big Sur. If you copy OCLP to a bootable
device, use the same partition as Big Sur (nothing else) !

- MASTER: HIGH SIERRA
- SLAVE : WINDOWS 10
- SLAVE : BIG SUR

If you use WIN or High Sierra, take the Apple Boot Loader (ALT Key on start) - that means
that the OCLP was not loaded automatically if you use the Apple Boot Picker before. Only if
you want to use Big Sur, you can boot into OCLP to get the driver support for 64 Bit BigSur.

The problem is that people mix the OCLP with native OS, then people become an "OPEN CORE"
definition of the machine, which means that native OS cannot identify exactly ALIAS which hardware
was inside !

- You don't need a GOP Injection if you have an EG BIOS patched MXM GPU.
- A machine with unsupported OCLP-macOS ONLY + OCLP-based detection of the AMD GPU
hardware are the solution from Big Sur to Sequoia - but I don't like it if that's not native...

 

[Yomaho]

Hello, you can use KEXTDrop App + added KEXT files to save this into S/L/E (System/Library/Extensions).
I hope, that are the right ones for High Sierra, additional Mojave & Catalina are zipped on my SSD.
If you can use that for AMD/ATI I don't know, that are I think only for NVIDIA Quadro + NVIDIA GTX 😊

I've read some of your previous posts to understand what your problem is...
Also you want to have WIN, 64Bit Big Sur and 32Bit High Sierra on one or
more HDD / SSD ?

It means:

- OCLP + Boot Loader is only the solution for 64Bit BigSur and unsupported OS (not Mojave / Catalina)
- 32Bit High Sierra is native, so you need only the KEXT Files -> save to S/L/E
- WIN (Legacy Mode installation - standalone) is native (no need of OCLP) !

Make 3x partitions, install High Sierra first (you only need the KEXT files -> Black screen patch),
then install WIN (Legacy mode - native) without OCLP, but - of course - all downloadable drivers
for the hardware, third you can install OCLP-patched 64Bit Big Sur. If you copy OCLP to a bootable
device, use the same partition as Big Sur (nothing else) !

- MASTER: HIGH SIERRA
- SLAVE : WINDOWS 10
- SLAVE : BIG SUR

If you use WIN or High Sierra, take the Apple Boot Loader (ALT Key on start) - that means
that the OCLP was not loaded automatically if you use the Apple Boot Picker before. Only if
you want to use Big Sur, you can boot into OCLP to get the driver support for 64 Bit BigSur.

The problem is that people mix the OCLP with native OS, then people become an "OPEN CORE"
definition of the machine, which means that native OS cannot identify exactly ALIAS which hardware
was inside !

- You don't need a GOP Injection if you have an EG BIOS patched MXM GPU.
- A machine with unsupported OCLP-macOS ONLY + OCLP-based detection of the AMD GPU
hardware are the solution from Big Sur to Sequoia - but I don't like it if that's not native...

Wooow, thank you very much for that detailed answer

Thanks for the Kext Loader, I just found it before, and i was able to mount the ApplGraphics and turn on the screen.
I wanted to try if windows 10 would be more stable without OCLP boot. But no

Because my real problem is to have windows 10 working well (to work on Revit).
Actually, I don't really need macOS at the moment, I just use it if I need something to set up to make windows 10 working (since one year I turned on OCLP Big Sur/Windows 10 and since few days I am trying with High Sierra : it changes nothing to Windows).
I upgraded the GPU on my iMac late 2009 27 (11,1) with a NVidia Quadro K4100M.

So, my problem is that Windows 10 works great in UEFI but I have random black screen on boot. Before log screen the screen remains black. Sometimes just my external screen work without mouse, sometimes everything is black and I need to force reboot (I just tried the Legacy install and it's worth).
In windows, mainly, the problem is the famous Event ID 14.
I have no ideas what I can do.

I am trying my last options and then I think I will sadly thrown that iMac to the trash. (Maybe that could finish with a hammer in the iMac haha )

 

[Pacific1972]

Wooow, thank you very much for that detailed answer

Thanks for the Kext Loader, I just found it before, and i was able to mount the ApplGraphics and turn on the screen.
I wanted to try if windows 10 would be more stable without OCLP boot. But no

Because my real problem is to have windows 10 working well (to work on Revit).
Actually, I don't really need macOS at the moment, I just use it if I need something to set up to make windows 10 working (since one year I turned on OCLP Big Sur/Windows 10 and since few days I am trying with High Sierra : it changes nothing to Windows).
I upgraded the GPU on my iMac late 2009 27 (11,1) with a NVidia Quadro K4100M.

So, my problem is that Windows 10 works great in UEFI but I have random black screen on boot. Before log screen the screen remains black. Sometimes just my external screen work without mouse, sometimes everything is black and I need to force reboot (I just tried the Legacy install and it's worth).
In windows, mainly, the problem is the famous Event ID 14.
I have no ideas what I can do.

I am trying my last options and then I think I will sadly thrown that iMac to the trash. (Maybe that could finish with a hammer in the iMac haha )

Hello, with the Quadro K4100 it's worth to get a HDMI Ghost Adapter which you can try to connect
with Thunderbolt II Adapter to one of the sockets of the A1312 (I don't know yet which one) to emulate
an external screen.

The other try is to make a power supply to inverter patch with 3V or 3.3V IC switch.

12V to 3.3V step-down power module + cable but perhaps no screen dimming anymore possible...
...that is of course reliable what kind of BIOS you have (GOP / EG2 / EG) !

...best thing is to buy a pc and sell all on ebay 😄😆😅

 

[Yomaho]

Hello, with the Quadro K4100 it's worth to get a HDMI Ghost Adapter which you can try to connect
with Thunderbolt II Adapter to one of the sockets of the A1312 (I don't know yet which one) to emulate
an external screen.

The other try is to make a power supply to inverter patch with 3V or 3.3V IC switch.

View attachment 2487946

View attachment 2487947

View attachment 2487948

12V to 3.3V step-down power module + cable but perhaps no screen dimming anymore possible...
...that is of course reliable what kind of BIOS you have (GOP / EG2 / EG) !

...best thing is to buy a pc and sell all on ebay 😄😆😅

Thanks for that proprosition but I won't go in such hardware job (too complicate for me)

Actually, I am wondering if it could be something about the flash ROM on the GPU. Maybe some compatibility troubles with windows.

 

[Nguyen Duc Hieu]

Thanks for that proprosition but I won't go in such hardware job (too complicate for me)

Actually, I am wondering if it could be something about the flash ROM on the GPU. Maybe some compatibility troubles with windows.

You mean that you haven't patched your Quadro K4100m with Mac compatible vBIOS?
In that case, the solution is much simpler: Below is the post with the vBIOS.

2011 iMac Graphics Card Upgrade

** NVIDIA Quadro K4100M Mac Edition ROM ** Genuine Native Boot Screen & Brightness Control After much testing and research, I've put together a ROM for the NVIDIA Quadro K4100M which will allow: Genuine native brightness control Genuine ‘gray’ early-boot screen Genuine macOS bootloader...

forums.macrumors.com

 

[Yomaho]

You mean that you haven't patched your Quadro K4100m with Mac compatible vBIOS?
In that case, the solution is much simpler: Below is the post with the vBIOS.

2011 iMac Graphics Card Upgrade

** NVIDIA Quadro K4100M Mac Edition ROM ** Genuine Native Boot Screen & Brightness Control After much testing and research, I've put together a ROM for the NVIDIA Quadro K4100M which will allow: Genuine native brightness control Genuine ‘gray’ early-boot screen Genuine macOS bootloader...

forums.macrumors.com

Thanks for your answer but the GPU was already flashed when I bought it. And I looked at it after install, and the good ROM was on.

What I mean is that may have something in the ROM interfering with windows ?
It's just a novice question because I don't understand what exactly is done in the UEFI boot.

But something is going wrong sometimes whereas the others times it's working great. Really strange ...
That's why I insist to use that iMac, because the system is enough for what I am doing and most of the time it's working well.
But the random black screen is frustrating. Sometimes I need something like 15 minutes to boot Windows with 3 or 4 hard restart.
So I would like to solve that problem but it seems to be complicated.

 

[Nguyen Duc Hieu]

Thanks for your answer but the GPU was already flashed when I bought it. And I looked at it after install, and the good ROM was on.

What I mean is that may have something in the ROM interfering with windows ?
It's just a novice question because I don't understand what exactly is done in the UEFI boot.

But something is going wrong sometimes whereas the others times it's working great. Really strange ...
That's why I insist to use that iMac, because the system is enough for what I am doing and most of the time it's working well.
But the random black screen is frustrating. Sometimes I need something like 15 minutes to boot Windows with 3 or 4 hard restart.
So I would like to solve that problem but it seems to be complicated.

I'm also a Windows user. The black-screen issue is quite common with Windows.
Sometimes removing the old driver and reinstall driver for GPU helps, sometimes it doesn't.
So you can try some tests to detect the issue:
1. Overheat GPU? => Do some GPU stress tests while monitoring GPU temperature.
2. Bad/corrupted GPU drivers? Remove the current drivers and install official drivers from NVDIA website. Hope you still can find them.
3. Black-screen because no signal, or black-screen because bad LCD backlight board? Verify that the backlight is still on when you have a black screen... It's rather subtle, but still distinguishable.

 

[Yomaho]

I'm also a Windows user. The black-screen issue is quite common with Windows.
Sometimes removing the old driver and reinstall driver for GPU helps, sometimes it doesn't.
So you can try some tests to detect the issue:
1. Overheat GPU? => Do some GPU stress tests while monitoring GPU temperature.
2. Bad/corrupted GPU drivers? Remove the current drivers and install official drivers from NVDIA website. Hope you still can find them.
3. Black-screen because no signal, or black-screen because bad LCD backlight board? Verify that the backlight is still on when you have a black screen... It's rather subtle, but still distinguishable.

1. Overheat GPU : I don't think so, I use macfanscontrol and so I manage temperature to never go more than 85 °C. Even in game or using 3D softwares it's alright. And, at the moment, i didn't replace the température sensor of the harddisk in the middle behind the screen, so at boot all my fans are at maximum (like a plane going to the moon )

2. I tried almost everything with GPU drivers : the ones given with Windows Update (The more stable I think) and then I tried different version given on nvidia website. At the moment, I am running with the last one from nvidia website, nothing change.
Also, each time I uninstall a driver I use DDU.

3. Here I have some changes. When I got the black screen problem there is no backlight (as you said it's subtle but I can distinguish it).
With windows in UEFI the most often windows can boot but on my external screen without mouse cursor. So I log on, I can see icons beeing highlited when mouse pass on them but can't see the cursor. So I use the shortcut Windows+P to access display settings and I select Duplicate. Then the intrenal iMac screen come back to life and I get back the mouse cursor (before my last reinstall I was just getting back mouse cursor without internal iMac screen).

Last thing I am on it is the BootRom of macOS. I remember that I upgraded as needed longtime ago.
I just looked at it and it's back to 63.0.0.0.0 on High Sierra. Maybe due to my several reinstallations.
So it seems too old for the vBIOS manipulation. I am trying to upgrade it but I don't remember how. I will look at that.
Even if I don't think it will change anything.

 

[Pacific1972]

1. Overheat GPU : I don't think so, I use macfanscontrol and so I manage temperature to never go more than 85 °C. Even in game or using 3D softwares it's alright. And, at the moment, i didn't replace the température sensor of the harddisk in the middle behind the screen, so at boot all my fans are at maximum (like a plane going to the moon )

2. I tried almost everything with GPU drivers : the ones given with Windows Update (The more stable I think) and then I tried different version given on nvidia website. At the moment, I am running with the last one from nvidia website, nothing change.
Also, each time I uninstall a driver I use DDU.

3. Here I have some changes. When I got the black screen problem there is no backlight (as you said it's subtle but I can distinguish it).
With windows in UEFI the most often windows can boot but on my external screen without mouse cursor. So I log on, I can see icons beeing highlited when mouse pass on them but can't see the cursor. So I use the shortcut Windows+P to access display settings and I select Duplicate. Then the intrenal iMac screen come back to life and I get back the mouse cursor (before my last reinstall I was just getting back mouse cursor without internal iMac screen).

Last thing I am on it is the BootRom of macOS. I remember that I upgraded as needed longtime ago.
I just looked at it and it's back to 63.0.0.0.0 on High Sierra. Maybe due to my several reinstallations.
So it seems too old for the vBIOS manipulation. I am trying to upgrade it but I don't remember how. I will look at that.
Even if I don't think it will change anything.

BIOS Upgrade for iMac:

EFI- und SMC-Firmware-Updates für Intel-basierte Mac-Computer - Apple Support (DE)

Dieser Artikel führt Firmware-Updates auf, die als eigenständige Installationsprogramme für Intel-basierte Mac-Computer erhältlich sind.

support.apple.com

The 85° Celsius is much too high ! Try to get 59° - 67° max. (before Apple Hardware shut down).
...sometimes it's better to take a K2100 ☺️ as using a barn heater like K4100 or GTX880 !

😄🤭

 

[Yomaho]

BIOS Upgrade for iMac:

EFI- und SMC-Firmware-Updates für Intel-basierte Mac-Computer - Apple Support (DE)

Dieser Artikel führt Firmware-Updates auf, die als eigenständige Installationsprogramme für Intel-basierte Mac-Computer erhältlich sind.

support.apple.com

The 85° Celsius is much too high ! Try to get 59° - 67° max. (before Apple Hardware shut down).
...sometimes it's better to take a K2100 ☺️ as using a barn heater like K4100 or GTX880 !

😄🤭

Yes I tried the update of BIOS from that link but doesn't work. Not good system specifications.

It never goes to 85°C, but I will check again. It's the temp of the heatsink not the processor one.

Maybe for the K2100 but with the K4100 I don't need no more heating for my house
That was the one I found easily, that was long seaches

 

[Guaika1]

Hello,

i don´t know if it is documented but for the problem associated with no ip from dhcp server when booting GRML from USB the problem for me was that date/time where loosed because CR2032 battery had been removed.

The way i found has been to install a working card and set correct date/time, install new card and boot from GRML again...

If helps someone...