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

[iPlasm]

So I think my OpenCore failure is indeed/most likely due to my 11,1 iMac's older Boot ROM version (currently IM111.0039.B00).

Current version of High Sierra: 10.13.6 (17G14033)

I've re-installed the latest 2020-005 Security Update, twice. Still no luck

Backup your files,
Get an older version of MacOS 10.13 High Sierra or the first version of MacOS 10.13.6, make a bootable Disk and then wipe format your Main HDD fully using bootable disk (remember to list all the disks in the hidden Disk Utility list), restart and do SMC and PRAM resets twice.... boot to Mac until you see a question marked folder, and then begin to boot MacOS Installation.
After installation, you may install older version of Security Updates or that 2020-005 update in order to able install the newer bootrom firmware version.
Signs like a tricks!

Have a good luck! 😇

 

[BeatCrazy]

Backup your files,
Get an older version of MacOS 10.13 High Sierra or the first version of MacOS 10.13.6, make a bootable Disk and then wipe format your Main HDD fully using bootable disk (remember to list all the disks in the hidden Disk Utility list), restart and do SMC and PRAM resets twice.... boot to Mac until you see a question marked folder, and then begin to boot MacOS Installation.
After installation, you may install older version of Security Updates or that 2020-005 update in order to able install the newer bootrom firmware version.
Signs like a tricks!

Have a good luck! 😇

Thank you.

After reading a bit around here, it seem like even re-installs don't wipe out the Boot ROM from some low-level part of the SSD. So here's what I did:

I installed a brand new SSD. Then, I installed the original 10.13.6 (17G66), from a recent bootable download which is Apple's original version from July 2018. After that, I went to the App Store, and got all the "cumulative" updates to the most current: Sept, 24, 2020.

Still no luck.

I suppose I could go all the way back to 10.13.2, and try to update via the App Store. I've got nothing to lose at this point.

 

[doscore]

Im now wondering if this card works in theory but we are the first to be trying it on a 2009. Seems like it has been tested on the 2011, and our lovely Ebay seller is making some assumptions. Their reply to me was "Maybe it is not compatible" and then sent me to this thread.

Seems like im not missing anything obvious so im likely just going to return them on monday if i cant work it out over the weekend.

Can anyone recommend a card that works on the 2009 27 i5? Ideally fully functional and stable. One iMac is mine, and the other is going to a customer that will not want to deal with any kernel panics/freezes/etc

well it works in high sierra.. no boot screens but yes.. most people are doing the 2011 models

 

[doscore]

Oh, yes! This was my fault. I used the kext I sent you with the iMacPro config.plist on the 0.6.0 image spoofing the correct board ID in advance. You may try this, again. You need to install the iMacPro1,1 AppleIntelSNBGraphicsFB.kext, too. Otherwise your system will not sleep. You find the files in the sleep post @highvoltage12v made.

Since I do not own a similar config any longer you have to test it on your own. I cannot cross check. Do not know it it is better than your solution.

Attached you will find the 12,1->iMacPro1,1 patched AppleIntelSNBGraphicsFB.kext (experimental).

Note:
Using the iMacPro1,1 ID effectively hides all black screen issues, too. As long you are using an AMD card with the OpenCore or this experimental Nvidia setting you will not see this. But there are currently three ways to solve this, installing a patched version of the AGC, using Lilu or spoofing the iMacPro1,1 ID.
If one reads the first 5 to 10 pages of this thread all can discover that the annoying black screen was a problem from day one on.
[automerge]1602831713[/automerge]

Did you even try to install the patched AGC? I doubt this because you asked for the 11,3 ID and you could have seen the answer when reading the post about this.

YES i have tried the patched AGC, the high sierra one works fine but the Catalina version does not. im just checking all the bases to make sure i have everything right is all

the fact that from windows i cannot even download the original rom means these cards are no good to me because the vbios is locked but it runs fine in high sierra

i did manage to get catalina to boot but the screen was black but i could still hear and use the computer via screen sharing... so WTF... and windows 7 boots fine full acceleration

but one card that successfully flashed and i already have the AGC kexts installed always gets stuck on a white or black screen and windows 7 will not even boot (only safe mode) with those kexts worked fine for the locked vbios cards

 

[Ryan001]

Is there a preference to having either Windows 7 or Windows 10 installed prior to the GPU swap? Does it even matter? Personally, I was thinking of upgrading to Windows 10 as it will be easier to remote in from my other Windows 10 computer in case there are any complications during flash/install.

 

[NewbiePete]

A question for the experienced among you ... is it absolutely necessary to connect the panel with its four plugs before switching on the iMac ??? Background to the question ... I would like to boot the iMac via USB stick with a Linux (for the purpose of nvflash etc.) ... but for obvious reasons I have to leave the internal boot devices disconnected. I don't want to burden the fragile connectors too much (I'm a little bit clumsy at times) ... oh, before you are asked, the USB Linux stick allows me to connect to SSH after booting.

Thanks in advance

greetings

Pete

 

[ZenSurfeur]

no need to connect the internal screen to flash the card using the usb @xanderon method

 

[BeatCrazy]

@iPlasm

Well I think I've really botched things. Although I have no problems creating the Catalina Loader (and even configuring the tweaks described by @Ausdauersportler and @herrdude here and here), I get a boot failure after I pick my Macintosh HD here:

The only way I can actually boot (because normally it's just black), is to hold down Option, then I can pick my Catalina boot drive. Of course, I don't have Brightness control, either.

As a reminder, my system is iMac 11,1 Late 2009 27" i7-860 + K2100M (helped with @Nick [D]vB tool). I've used DOSdude1's Catalina Patcher, and that seemed to work out just fine.

My BootROM is still IM111.0039.B00 (4 April 2018 version). I don't think there is any newer version for the iMac11,1. I see people say it should be 63.0.0.0.0, but I'm fairly sure now that there is no way to get this on my system. I did fresh installs of High Sierra and even El Capitan (both from official bootable USBs), onto two different/fresh internal SSDs and even a standard internal HDD. I wanted to make sure the system wasn't balking by not "seeing" a standard HDD like it came with originally. Using the App Store, I grabbed the latest 2020-005 Security Updates for High Sierra, and that did not change my EFI/BootROM.

At this point, I just gave up on getting a different BootROM, and just used the Catalina Patcher. But I still cannot use OpenCore. Resetting PRAM doesn't help.

Any help is appreciated. I think I have really explored every single option. Read every single post.

 

[ezugaru]

@iPlasm

Well I think I've really botched things. Although I have no problems creating the Catalina Loader (and even configuring the tweaks described by @Ausdauersportler and @herrdude here and here), I get a boot failure after I pick my Macintosh HD here:

The only way I can actually boot (because normally it's just black), is to hold down Option, then I can pick my Catalina boot drive. Of course, I don't have Brightness control, either.

As a reminder, my system is iMac 11,1 Late 2009 27" i7-860 + K2100M (helped with @Nick [D]vB tool). I've used DOSdude1's Catalina Patcher, and that seemed to work out just fine.

My BootROM is still IM111.0039.B00 (4 April 2018 version). I don't think there is any newer version for the iMac11,1. I see people say it should be 63.0.0.0.0, but I'm fairly sure now that there is no way to get this on my system. I did fresh installs of High Sierra and even El Capitan (both from official bootable USBs), onto two different/fresh internal SSDs and even a standard internal HDD. I wanted to make sure the system wasn't balking by not "seeing" a standard HDD like it came with originally. Using the App Store, I grabbed the latest 2020-005 Security Updates for High Sierra, and that did not change my EFI/BootROM.

At this point, I just gave up on getting a different BootROM, and just used the Catalina Patcher. But I still cannot use OpenCore.

Any help is appreciated. I think I have really explored every single option. Read every single post.

Check this:

How to upgrade boot rom firmware without an original drive

I have a 2015 MacBook pro that I am in the process of refurbishing. I purchased it used and it was missing many parts (wifi card, IO board, SSD). I have replaced all of these parts and purchased an

apple.stackexchange.com

 

[BeatCrazy]

Check this:

How to upgrade boot rom firmware without an original drive

I have a 2015 MacBook pro that I am in the process of refurbishing. I purchased it used and it was missing many parts (wifi card, IO board, SSD). I have replaced all of these parts and purchased an

apple.stackexchange.com

Thank you. However, I did try to use a standard HDD. Not sure if I should be trying to find an "original" Apple HDD? Not sure how I would ID the correct one that would guaranty a correct update, but info is appreciated. My volume is APFS, and that wouldn't pull down a newer version, either.

 

[Ausdauersportler]

Chicken or Egg Dilemma with Nvidia cards
and late iMac 27 2009
​

Yesterday I tried to install a K4100M in my late 2009 and made the following experience. On boot system came up with working internal LCD, however after a PRAM reset the internal LCD remained dark and only three LED came up.

After connecting an external display I got the boot screen on alt/option only on the external display, the internal remained dark. Booting into Catalina or High Sierra worked fine. The internal LCD did not work.

After installing the patched AGC and after booting into the MacOS with the patched AGC the internal LCD came up and stayed in function. Even after a power off and power on. After deleting the PRAM I got the same not working internal LCD, again.

So users with the iMac 27 2009 may face the Chicken and Egg Dilemma. Without a working display no MacOS installation with the patched AGC possible.

You need an external display or a second Apple system to prepare a MacOS installation having the patched AGC. Possibly one can prepare such an bootable MacOS on an 32GB SD card only for this purpose.



Notes:
Did not test this with different Nvidia cards and currently not on an 2010 system.
Did no checks on the NVRAM contents right now.
Patched AGC - see post #1 for the black screen issue.

EDIT:
Installing OpenCore through OCLP solves this issue, too!

 

[BeatCrazy]

Chicken or Egg Dilemma with (some) Nvidia cards
and late iMac 27 2009
​

Yesterday I tried to install a K4100M in my late 2009 and made the following experience. On boot system came up with working internal LCD, however after a PRAM reset the internal LCD remained dark and only three LED came up.

After connecting an external display I got the boot screen on alt/option only on the external display, the internal remained dark. Booting into Catalina or High Sierra worked fine. The internal LCD did not work.

After installing the patched AGC and after booting into the MacOS with the patched AGC the internal LCD came up and stayed in function. Even after a power off and power on. After deleting the PRAM I got the same not working internal LCD, again.

So users with the iMac 27 2009 may face the Chicken and Egg Dilemma. Without a working display no MacOS installation with the patched AGC possible.

You need an external display or a second Apple system to prepare a MacOS installation having the patched AGC. Possibly one can prepare such an bootable MacOS on an 32GB SD card only for this purpose.



Notes:
Did not test this with different Nvidia cards and currently not on an 2010 system.
Did no checks on the NVRAM contents right now.
Patched AGC - see post #1 for the black screen issue.

Question: Who can confirm this behaviour?

Please report back system and card type and please, please add a signature to your account showing hardware and OS, too (if not already done).

I can help. I want to patch AGC, and I see instructions in this post. I see that I should be using the Kext Utility from that RU site, however it looks like is only for patching Sierra kexts? I'm installing a fresh copy of Catalina right now.

My card is the K2100M, already flashed and working. Except no boot screen or native brightness, of course.

 

[iPlasm]

Thank you.

After reading a bit around here, it seem like even re-installs don't wipe out the Boot ROM from some low-level part of the SSD. So here's what I did:

I installed a brand new SSD. Then, I installed the original 10.13.6 (17G66), from a recent bootable download which is Apple's original version from July 2018. After that, I went to the App Store, and got all the "cumulative" updates to the most current: Sept, 24, 2020.

Still no luck.

I suppose I could go all the way back to 10.13.2, and try to update via the App Store. I've got nothing to lose at this point.

Wiping HDD won't wipe Boot ROM firmware, the important is the OS and Cache are wiped totally for starting fresh and new certification signs.
I don't think the SSD disallows to install the firmware, I had replaced my Main HDD to FireCuda 3.5" (APFS formatted) four years ago even without Fan OWC sensor (which shows error in Apple Diagnostic Test) and I'm on latest (Boot ROM Version: 87.0.0.0.0) in my iMac 2011 21.5".
I don't want make it complex for you, but from what I've read in web, the secret is it's hidden one by one....
For example if you jump from MacOS 10.10 to 10.12, you may lose the firmware update (unless if Apple made this smart to install the firmware), you've to or you may install this one by one 10.10.1> 10.10.2> 10.10.3> 10.10.4.........>.and so on...>>..>.
The mentioned Combo updates should work, but sometimes it may not include the firmware in that package

What you've to know that is hidden and secret. So first do the easy and then the long way. I had these experience for a long time when I was a Child which I were installing OSes and firmwares... and more worse it may suddenly get bricked (rarely) for unknown reason, it's totally sad moments.

Try to read these carefully, this will help you alot.
https://eclecticlight.co/2018/06/27/which-efi-firmware-should-your-mac-be-using-version-2/
https://eclecticlight.co/2018/10/31/which-efi-firmware-should-your-mac-be-using-version-3/

Apple's politic is that you update and never revert back! like iPhones, it won't let you downgrade! and it made some changes to Macs too.

I don't have any more ideas for you right now, but you may ask and we will welcome
Good luck!

Check this:

How to upgrade boot rom firmware without an original drive

I have a 2015 MacBook pro that I am in the process of refurbishing. I purchased it used and it was missing many parts (wifi card, IO board, SSD). I have replaced all of these parts and purchased an

apple.stackexchange.com

From what've I read in this, I guess it's rare? more knowledge information needed

 

[ezugaru]

Wiping HDD won't wipe Boot ROM firmware, the important is the OS and Cache are wiped totally for starting fresh and new certification signs.
I don't think the SSD disallows to install the firmware, I had replaced my Main HDD to FireCuda 3.5" (APFS formatted) four years ago even without Fan OWC sensor (which shows error in Apple Diagnostic Test) and I'm on latest (Boot ROM Version: 87.0.0.0.0) in my iMac 2011 21.5".
I don't want make it complex for you, but from what I've read in web, the secret is it's hidden one by one....
For example if you jump from MacOS 10.10 to 10.12, you may lose the firmware update (unless if Apple made this smart to install the firmware), you've to or you may install this one by one 10.10.1> 10.10.2> 10.10.3> 10.10.4.........>.and so on...>>..>.
The mentioned Combo updates should work, but sometimes it may not include the firmware in that package

What you've to know that is hidden and secret. So first do the easy and then the long way. I had these experience for a long time when I was a Child which I were installing OSes and firmwares... and more worse it may suddenly get bricked (rarely) for unknown reason, it's totally sad moments.

Try to read these carefully, this will help you alot.
https://eclecticlight.co/2018/06/27/which-efi-firmware-should-your-mac-be-using-version-2/
https://eclecticlight.co/2018/10/31/which-efi-firmware-should-your-mac-be-using-version-3/

Apple's politic is that you update and never revert back! like iPhones, it won't let you downgrade! and it made some changes to Macs too.

I don't have any more ideas for you right now, but you may ask and we will welcome
Good luck!


From what've I read in this, I guess it's rare? more knowledge information needed

It might be rare because we are talking about a computer....but for other devices some companies do exactly that.

I am a technician for MultiFunction Printers, such Konica Minolta, when You replace a board, it Will come with the first version of firmware released, no matter what, the problem is that de logic board and control board are "married", so both share the firmware version, if there is a missmatch then you get a error code and can't use the MFP. Then you have to manually update the firmware, one by one....imagine the happiness when You see like 15 releases...if You go right to the last one the firmware ends corrupted so You need yo start over again...

 

[BeatCrazy]

Wiping HDD won't wipe Boot ROM firmware, the important is the OS and Cache are wiped totally for starting fresh and new certification signs.
I don't think the SSD disallows to install the firmware, I had replaced my Main HDD to FireCuda 3.5" (APFS formatted) four years ago even without Fan OWC sensor (which shows error in Apple Diagnostic Test) and I'm on latest (Boot ROM Version: 87.0.0.0.0) in my iMac 2011 21.5".
I don't want make it complex for you, but from what I've read in web, the secret is it's hidden one by one....
For example if you jump from MacOS 10.10 to 10.12, you may lose the firmware update (unless if Apple made this smart to install the firmware), you've to or you may install this one by one 10.10.1> 10.10.2> 10.10.3> 10.10.4.........>.and so on...>>..>.
The mentioned Combo updates should work, but sometimes it may not include the firmware in that package

What you've to know that is hidden and secret. So first do the easy and then the long way. I had these experience for a long time when I was a Child which I were installing OSes and firmwares... and more worse it may suddenly get bricked (rarely) for unknown reason, it's totally sad moments.

Try to read these carefully, this will help you alot.
https://eclecticlight.co/2018/06/27/which-efi-firmware-should-your-mac-be-using-version-2/
https://eclecticlight.co/2018/10/31/which-efi-firmware-should-your-mac-be-using-version-3/

Apple's politic is that you update and never revert back! like iPhones, it won't let you downgrade! and it made some changes to Macs too.

I don't have any more ideas for you right now, but you may ask and we will welcome
Good luck!


From what've I read in this, I guess it's rare? more knowledge information needed

I appreciate the links. I found them earlier today, and they were the motivation for me trying to start with a fresh HDD (not SSD) in attempts to convince the iMac that it was in a "more original" state and force a BootROM update as I updated via official installers. I started with El Capitan, then to the initial 10.13.6, then finally 10.13.6 with all patches included Security Update 2020-005.

I'm a patient guy, but I definitely don't feel like updating through all point releases since 10.7

I'm starting to think that although my graphics card update to the K2100M was physically successful, if I can't get a boot screen and native brightness, it was all for nothing

 

[ezugaru]

I appreciate the links. I found them earlier today, and they were the motivation for me trying to start with a fresh HDD (not SSD) in attempts to convince the iMac that it was in a "more original" state and force a BootROM update as I updated via official installers. I started with El Capitan, then to the initial 10.13.6, then finally 10.13.6 with all patches included Security Update 2020-005.

I'm a patient guy, but I definitely don't feel like updating through all point releases since 10.7

I'm starting to think that although my graphics card update to the K2100M was physically successful, if I can't get a boot screen and native brightness, it was all for nothing

I was remembering somerthing i learnt during My HP certification, maybe it is similar to this case...
In HP MFPs, the place where the firmware its stored has some kind of partitions, so there are segments of the firmware for each hardware level components of the device....so the logic board has its corresponding firmware portion in one place, the control board in another, the scanner in another, the Automatic Document Feeder in another and so on.
The thing is , firmware releases arent incremental....maybe in versión 1.0.1 there was a fix for the scanner, and the release 1.0.2 has a fix for the control board, but it doesnt have the fix for the scanner the previous versión has...this means that at some point You might end with error codes because maybe you skipped a critical upgrade that was needed for a future feature and now there device has a corrupted firmware ...
Remember, this is just an opinion and i don't have evidence this is the case.

 

[GCtravellerguy]

I have a 2010 Imac 27" installed the K1100m did the program all worked well until So I did the Linux flash and thought I had completed everything until I put the lcd panel pack in and tried to start up and was faced with a black screen... I tried the boot holding option key and was confronted with this help

 

[Wania]

Chicken or Egg Dilemma with (some) Nvidia cards
and late iMac 27 2009
​

Yesterday I tried to install a K4100M in my late 2009 and made the following experience. On boot system came up with working internal LCD, however after a PRAM reset the internal LCD remained dark and only three LED came up.

After connecting an external display I got the boot screen on alt/option only on the external display, the internal remained dark. Booting into Catalina or High Sierra worked fine. The internal LCD did not work.

After installing the patched AGC and after booting into the MacOS with the patched AGC the internal LCD came up and stayed in function. Even after a power off and power on. After deleting the PRAM I got the same not working internal LCD, again.

So users with the iMac 27 2009 may face the Chicken and Egg Dilemma. Without a working display no MacOS installation with the patched AGC possible.

You need an external display or a second Apple system to prepare a MacOS installation having the patched AGC. Possibly one can prepare such an bootable MacOS on an 32GB SD card only for this purpose.



Notes:
Did not test this with different Nvidia cards and currently not on an 2010 system.
Did no checks on the NVRAM contents right now.
Patched AGC - see post #1 for the black screen issue.

Question: Who can confirm this behaviour?

Please report back system and card type and please, please add a signature to your account showing hardware and OS, too (if not already done).

I had the same situation on my iMac 2009 27 with the K5000M card, I used the K2100M back

 

[Underbeat88]

Hello Guys. Your help is very much needed. I recently upgraded my iMac 27 2011 from GTX 765 to K4100M, in Windows Device Manager I deleted the previous video card and driver to update it to the new driver, but now the new video card is not showing and I cannot install the new driver as the driver cannot find suitable devices((( Help please.

 

[iPlasm]

It might be rare because we are talking about a computer....but for other devices some companies do exactly that.

I am a technician for MultiFunction Printers, such Konica Minolta, when You replace a board, it Will come with the first version of firmware released, no matter what, the problem is that de logic board and control board are "married", so both share the firmware version, if there is a missmatch then you get a error code and can't use the MFP. Then you have to manually update the firmware, one by one....imagine the happiness when You see like 15 releases...if You go right to the last one the firmware ends corrupted so You need yo start over again...

I was remembering somerthing i learnt during My HP certification, maybe it is similar to this case...
In HP MFPs, the place where the firmware its stored has some kind of partitions, so there are segments of the firmware for each hardware level components of the device....so the logic board has its corresponding firmware portion in one place, the control board in another, the scanner in another, the Automatic Document Feeder in another and so on.
The thing is , firmware releases arent incremental....maybe in versión 1.0.1 there was a fix for the scanner, and the release 1.0.2 has a fix for the control board, but it doesnt have the fix for the scanner the previous versión has...this means that at some point You might end with error codes because maybe you skipped a critical upgrade that was needed for a future feature and now there device has a corrupted firmware ...
Remember, this is just an opinion and i don't have evidence this is the case.

Exactly, you're right.... perfectly what I meant
However we're talking about possibilities and options to all people (we and as my experience), since it should be done and fixed unless a faulty hardware or for unknown reason.

I appreciate the links. I found them earlier today, and they were the motivation for me trying to start with a fresh HDD (not SSD) in attempts to convince the iMac that it was in a "more original" state and force a BootROM update as I updated via official installers. I started with El Capitan, then to the initial 10.13.6, then finally 10.13.6 with all patches included Security Update 2020-005.

I'm a patient guy, but I definitely don't feel like updating through all point releases since 10.7

I'm starting to think that although my graphics card update to the K2100M was physically successful, if I can't get a boot screen and native brightness, it was all for nothing

Of course, it sounds crazy starting from OS 10.7 (or maybe older) and then step by step updates to High Sierra, about more than 30 packages installations! 😝 and remember this is the longest way, so start with easy one (such as checking firmware version and certifications and using terminal codes....etc), try to let apple's package to install the firmware, doing manually can be risky.
if you don't succeed this long step by step updates, then your next would be a Hardware thing.
Have a good luck 😇

 

[BertHiddink]

@BertHiddink
There is no such card as a "GTX745M". The card that you have a picture of in your post is actually indeed a GTX765M, the GPU variant information is: N14E-GE-B-A1. There was only a GT 745M made which was part of a logic board installation.

Hello nikey22,

Yes I became aware of that! I could succesfully install the card on a iMac 2011 27"!
Thanks!

 

[BeatCrazy]

Of course, it sounds crazy starting from OS 10.7 (or maybe older) and then step by step updates to High Sierra, about more than 30 packages installations! 😝 and remember this is the longest way, so start with easy one (such as checking firmware version and certifications and using terminal codes....etc), try to let apple's package to install the firmware, doing manually can be risky.
if you don't succeed this long step by step updates, then your next would be a Hardware thing.
Have a good luck 😇

What is the "hardware thing" you're referring to?

I've already tried starting at El Capitan with a new/fresh HDD, then move to High Sierra. Also of note: when installing the latest 2020-005 patch to High Sierra, my machine does make that long beeeeep that indicates it's updating it's firmware. But after that, it does seem to stay "off" until I press the power button to complete the installation.

100% back on subject (all my post are always related to getting my updated K2100M working correctly )... I did notice that the K2100M did not play nice with Catalina. When clicking on windows, the bar at the top would often turn black, and dragging windows would leave multiple versions/stutters of the same window where you dragged it. Hard to describe, but something is not working correctly.

 

[iPlasm]

What is the "hardware thing" you're referring to?

I've already tried starting at El Capitan with a new/fresh HDD, then move to High Sierra. Also of note: when installing the latest 2020-005 patch to High Sierra, my machine does make that long beeeeep that indicates it's updating it's firmware. But after that, it does seem to stay "off" until I press the power button to complete the installation.

100% back on subject (all my post are always related to getting my updated K2100M working correctly )... I did notice that the K2100M did not play nice with Catalina. When clicking on windows, the bar at the top would often turn black, and dragging windows would leave multiple versions/stutters of the same window where you dragged it. Hard to describe, but something is not working correctly.

By which way did you install El Capitan to high sierra? single click Combo update? (10.11.0 to 10.13.6) if that then no, you may need to install step by step, like from to 10.11.0 to 10.11.1>10.11.2>10.11.3>.... and so on...

Hardware thing, an example possible this can be the new nVidia GPU you installed may prevent your iMac to get update firmware.

 

[Ed Hartouni]

I have a 2010 Imac 27" installed the K1100m did the program all worked well until So I did the Linux flash and thought I had completed everything until I put the lcd panel pack in and tried to start up and was faced with a black screen... I tried the boot holding option key and was confronted with this help

Had a similar symptom on my initial attempt to install a K1100M in my 21.5" iMac mid 2011.
I took the system apart, replaced the K1100M with the original, working AMD gpu, and everything was OK, confirming that I did not break something in the disassembly-assembly process...
Turns out that the first K1100M I received was not working. The second one did work, here is the forum entry from the first attempt:

well, something went wrong... maybe someone here will recognize the issue...
iMac mid 2011 21.5"
attempted to replace with a Nvidia Quadro K1100M
using the "Linux stick" method,

Storing updated firmware image...
................................................................
Verifying update...
Update successful.

Firmware image has been updated from version Unavailable (Invalid) to DE.AD.00.BE.EF.


A reboot is required for the update to take effect.
./nvflash_linux -6 Quadro_Beta1.2/K1100.rom 48.13s user 2.65s system 58% cpu 1:27.54 total

when I reattached the internal disks and booted, I got this screen, which is a stalled bootup:
View attachment 944771

so something wasn't happy...
I did reset the NVRAM a couple of times, but that didn't help this...

I did get the boot disk screen, and I did select a disk... just that the screen isn't playing well with the card...

any suggestions?

The used cards are taken from machines that are not working and are being recycled, the reason those machines were retired are not generally known to the buyers... failed gpu's are certainly a reason to retire a machine.

Right now I'm running Catalina (with some interesting glitches...) and playing around with the Catalina Metal software on the K1100M.

 

[herrdude]

Had a similar symptom on my initial attempt to install a K1100M in my 21.5" iMac mid 2011.
I took the system apart, replaced the K1100M with the original, working AMD gpu, and everything was OK, confirming that I did not break something in the disassembly-assembly process...
Turns out that the first K1100M I received was not working. The second one did work, here is the forum entry from the first attempt:



The used cards are taken from machines that are not working and are being recycled, the reason those machines were retired are not generally known to the buyers... failed gpu's are certainly a reason to retire a machine.

Just throwing out ideas, have you tried installing by using CMD + R?