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

[BadBiscuit]

You're right,
It's 2 heatpipe but it's still MXM-B. I can't find any 3 heatpipe MXM-B heatsinks for sale. They still have cards attached to them and want obscene amounts of money for what is basically hot garbage. A 2 pipe MXM-B heatstink is still better than an MXM-A heatsink as there are components that need to be covered for cooling.

Sorry to be so late to the party on this, but just wanted to add a suggestion for acquiring 3-pipe heatsinks. Search for "6970" cards listings as "parts only" and look for heatsinks in the pictures. That tends to find the best price. I just picked up two more in the same way, so now all of my 27" machines can have one. I paid under $50 in each case. Make an offer and suggest they keep the 6970 and re-list it. Here is the listing for the ones I just bought, and the seller still has one left in case someone is looking:

AMD Radeon HD 6970M 1GB Video Graphics Card For Parts Not Working | eBay
Condition is For parts or not working.

Even though I offered to let him keep the cards, he sent them, so now I have two bad 6970M cards to dispose of. Not sure if there is any market for them, especially not knowing their history, but the heatsinks (which I'm keeping) are top notch. If anyone here wants a bad 6970M card (or two), they can have them for the cost of postage. Just PM me.

 

[RationalOne]

Well, sad news. I assumed something and once again it proves why I never assume anything.

I ordered a 3000m and not a K3000m. No metal support I'm told. Which was the whole point of this exercise.

Yes. I knew I needed a k3000m. Yes I read the 1st post. Yes I verified the chip was an N12E-Q1-A1.

But then made the leap to 'that cheap $25 3000m on ebay must just be so cheap because it doesn't yet have bios support for us imac people yet.'. And 'It's the exact same chip N12E-Q1-A1 mentioned by @nikey22 so that must be it!'. Nope.

Note to self: Again. Never assume. Every detail matters. You know this. Don't do it again. Even though I do it from time to time still when I get lazy. Lazy = costly in time, effort and money.

Hope this helps out those who come after me. Including my future self.

Also, just to share more lessons learned, I spent 45 minutes last night with a dremel enlarging the heatsink. Bit finally broke and I was still only half way done. It must have been too dull to be efficient. Today I just used a full sized grinder/cutter and did the whole thing in 3-5 minutes. Not pretty, but functional.

I'll attach pictures below for others' benefit.

Lastly, I'm also told by a member here that the k3000m ROM on this thread is not really for us imac 2009 guys and won't work anyway? I'd not read that specifically yet in the thread. I know the title of this thread is 2011 models, but I've seen a ton of overlap posted within. I could have sworn I'd read these roms were fine for the 2009 imac models too, no?

Since there is no specific thread for the 2009 models I guess I've 'assumed' again. I thought that this thread was the sole and best source of info for me and that this would work fine for my 2009 model but I've been told the roms are not the same. Would love a reconfirmation on that if someone knows. Not that I doubt him really. Just need to hear it again as it's more bad news if so. And I wanted to make sure I posted it for reference by others as I was missing that point.

On a positive note, he is offering to help me learn the art of rom extraction and editing for my 2009 though so that's encouraging. Now just to order an ch341a eprom burner and correct card. I'm still thinking a k3000m but am open to suggestions on the best value to go with considering I'm only after metal support for Mojave and not gaming.

Thanks everyone. I've appreciated the posts here in the thread, the PMs and the diligence and time you all share so we can succeed with these unsupported cards.

Learning.

Edit: I think I found the answer to the question on the 2009 models not working with these ROMs. It's actually only the core 2 duo models that can't work according to this note on page 1:

"The modified (video) BIOS version made by @Nick [D]vB, @nikey22 and @internetzel require an Intel i3 CPU or better. There is currently no way to make the features of these VBIOS working on Core 2 Duo systems (late 2009)."

I think I'm safe here as I have an i7 and page one does say 2009-2011 models.

 

[RationalOne]

Also, I wanted to put out a special thank you to @Ausdauersportler for all your efforts here in this thread. I can see how frustrated you are when people are not listening and can empathize. So I just wanted to take a minute to thank you for your continued diligence and adherence to attention to detail. Even when we aren't always listening or reading carefully enough. Thank you for your dedication.

Same thanks to others here with the same level of assistance for us. I appreciate it. Hope it helps a bit.

 

[marathonbiker]

Thank you for all the hard work in making these upgrades possible. I have my mid-2011 27" with a GTX 765M vbios flashed and working with Catalina 10.15.6. Of note if anyone runs into issues with only getting the 1st LED to light up and no others it may be due to grounding out of the video card. I did not grind down the heatsink at first, after a couple of days of trying SMC and NVRAM resets I took it all apart, used a Dremel on the heatsink and put it back together. Immediately worked, it was misleading at first because it would work intermittently causing me to doubt what was causing the problem.

I'm struggling with the kext installation now, I get the black screen on boot and need to press option key to load Catalina. I've installed Hackintool, downloaded the kext from this post, run the specified comments from terminal (sudo mount -uw / and killall Finder). I go to Hackintool to the utilities and select kexts, I choose the AppleGraphicsControl.kext and select /System/Library/Extensions as the path for destination and let Hackintool Rebuild KextCache and Repair Permissions. After its complete I sudo reboot. I get the black screen after reboot and power off, power on pressing Option key and can boot into Catalina using the boot switcher.

What am I doing wrong? Could anyone graciously provide step by step directions for the Kext install? So close to being complete!!

Thank you!
John

 

[marathonbiker]

Thank you for all the hard work in making these upgrades possible. I have my mid-2011 27" with a GTX 765M vbios flashed and working with Catalina 10.15.6. Of note if anyone runs into issues with only getting the 1st LED to light up and no others it may be due to grounding out of the video card. I did not grind down the heatsink at first, after a couple of days of trying SMC and NVRAM resets I took it all apart, used a Dremel on the heatsink and put it back together. Immediately worked, it was misleading at first because it would work intermittently causing me to doubt what was causing the problem.

I'm struggling with the kext installation now, I get the black screen on boot and need to press option key to load Catalina. I've installed Hackintool, downloaded the kext from this post, run the specified comments from terminal (sudo mount -uw / and killall Finder). I go to Hackintool to the utilities and select kexts, I choose the AppleGraphicsControl.kext and select /Library/Extensions as the path for destination and let Hackintool Rebuild KextCache and Repair Permissions. After its complete I sudo reboot. I get the black screen after reboot and power off, power on pressing Option key and can boot into Catalina using the boot switcher.

What am I doing wrong? Could anyone graciously provide step by step directions for the Kext install? So close to being complete!!

Thank you!
John

Okay, I found the guide (posted from page 1 for to fix sleep, airplay and intel QuickSync) and completed the instructions for those fixes as well as applying the AppleGraphicsControl.kext from this post. Now everything works for me with no black screen on power on, reboot, etc. Thank you everyone that has contributed to this entire thread, amazing to revive life into these older iMacs.

 

[Pascal Baillargeau]

Thank you for all the hard work in making these upgrades possible. I have my mid-2011 27" with a GTX 765M vbios flashed and working with Catalina 10.15.6. Of note if anyone runs into issues with only getting the 1st LED to light up and no others it may be due to grounding out of the video card. I did not grind down the heatsink at first, after a couple of days of trying SMC and NVRAM resets I took it all apart, used a Dremel on the heatsink and put it back together. Immediately worked, it was misleading at first because it would work intermittently causing me to doubt what was causing the problem.

I'm struggling with the kext installation now, I get the black screen on boot and need to press option key to load Catalina. I've installed Hackintool, downloaded the kext from this post, run the specified comments from terminal (sudo mount -uw / and killall Finder). I go to Hackintool to the utilities and select kexts, I choose the AppleGraphicsControl.kext and select /Library/Extensions as the path for destination and let Hackintool Rebuild KextCache and Repair Permissions. After its complete I sudo reboot. I get the black screen after reboot and power off, power on pressing Option key and can boot into Catalina using the boot switcher.

What am I doing wrong? Could anyone graciously provide step by step directions for the Kext install? So close to being complete!!

Thank you!
John

you mean "/System/Library/Extensions" ?

 

[Ausdauersportler]

Also, I wanted to put out a special thank you to @Ausdauersportler for all your efforts here in this thread. I can see how frustrated you are when people are not listening and can empathize. So I just wanted to take a minute to thank you for your continued diligence and adherence to attention to detail. Even when we aren't always listening or reading carefully enough. Thank you for your dedication.

Same thanks to others here with the same level of assistance for us. I appreciate it. Hope it helps a bit.

Thank you!

But I am in the most cases only the editor or messenger. The real work has been done during the last years and last months by the guys mentioned on page one and post one - the BIOS programmers. Without their work we would have nothing to play with.

Talking about recent questions:

Please do not open private conversations about general topics or private installation problems, i.e. Big Sur installation and K3100M target disk mode. I cannot help with both, have simply never used TDM before or cannot spend more time as I already put into this. Trust me, if I find something worth to post and document you will get a message and most likely another widely unread documentation PDF

 

[Ausdauersportler]

Well, sad news. I assumed something and once again it proves why I never assume anything.

I ordered a 3000m and not a K3000m. No metal support I'm told. Which was the whole point of this exercise.

I think I'm safe here as I have an i7 and page one does say 2009-2011 models.

You are using a big MXM B type 2009 or 2010 2 pipe heat sink. Interesting to see if this works out on the long run. I never found the TPD of the 4850 or 5850 cards used on this sink type before, but I assume that Apple changed the hardware design of the sink with the 6970M card for a reason. All MXM-B Nvidia cards listed on page will draw the same power as the 6970M on average and according to some widely unknown laws of physics (which cannot be bent by people) it will create heat in the same amount.

The K3000M rom has been pulled back, it is not stable and does not work properly. The safest bet is currently to go with the K3100M. Never let yourself drive into a deal just by low acquisition costs, the cost of ownership will eat up your budget. It is not worth to buy a cheap card which cannot run in the iMac. For this reason we created this nice table on page one.

 

[seefew]

Hi there,
I have an A1312 iMac (Mid2011), in the past few years I've installed a bunch of hardware goodies (CPU, RAM, etc).
The next or maybe last step before retirement is a "new" GPU for metal support and Mojave or Catalina
As read in Post #1, the K2100M is predestined to do this job in the iMac
I also own a HP ZBook 15 with a K2100M that I plan to replace with a M1000M (got it very cheap)
I've read here a lot about how to flash it in the iMac using Linux or Win or ssh etc.
my question is:
Are there any known issues with flashing while the GPU is in the ZBook?
It would be a lot easier, wouldn't it?
Thanks for reading
Greets
seefew

 

[Ausdauersportler]

Hi there,
I have an A1312 iMac (Mid2011), in the past few years I've installed a bunch of hardware goodies (CPU, RAM, etc).
The next or maybe last step before retirement is a "new" GPU for metal support and Mojave or Catalina
As read in Post #1, the K2100M is predestined to do this job in the iMac
I also own a HP ZBook 15 with a K2100M that I plan to replace with a M1000M (got it very cheap)
I've read here a lot about how to flash it in the iMac using Linux or Win or ssh etc.
my question is:
Are there any known issues with flashing while the GPU is in the ZBook?
It would be a lot easier, wouldn't it?
Thanks for reading
Greets
seefew

The HP laptop have dual GPU, manage the video BIOS from the internal laptop firmware. So I would assume you can flash and even use the K2100M within the HP laptop and change it later into the iMac. Worst case is the laptop will not switch to the K2100M GPU under load after flashing, but I would bet that will not happen. I said bet..

 

[seefew]

Thx for your response @Ausdauersportler
sounds good, i think i'll do it soon
pls don’t think I’m too stupid for that, I’ve done it several times with other cards and devices
but recently i've flashed a K610M in my other Laptop(XMG) and it went sadly wrong
Before flashing it was a working HP N15M-Q2-B-A1 and now it's a pretty but worthless Decoration.
I've tryed to flash the backup back with the XMG, a Computer with a MXM to PCIe Adapter and with a CH341A but nothing works neither in Linux nor Win
i knew the N15M-Q2-B-A1 isn't listed as *working*, but i've lying it around so i thougt, let's try
and I don't want to make the same Error twice

 

[Ausdauersportler]

Thx for your response @Ausdauersportler
sounds good, i think i'll do it soon
pls don’t think I’m too stupid for that, I’ve done it several times with other cards and devices
but recently i've flashed a K610M in my other Laptop(XMG) and it went sadly wrong
Before flashing it was a working HP N15M-Q2-B-A1 and now it's a pretty but worthless Decoration.
I've tryed to flash the backup back with the XMG, a Computer with a MXM to PCIe Adapter and with a CH341A but nothing works neither in Linux nor Win
i knew the N15M-Q2-B-A1 isn't listed as *working*, but i've lying it around so i thougt, let's try
and I don't want to make the same Error twice

Honestly, why you are asking here to do this if you already have a CH341A in place? The safest way to flash cards is using the clip, cards having WSON type chips need a software tool, my first choice is @xanderon's Linux USB version.

From my last check of the first post the K610M was perfectly working. Have you checked this post, lately? Have you used the correct BIOS?

 

[marathonbiker]

you mean "/System/Library/Extensions" ?

Yes, I updated my post to be accurate. Thanks for the catch!

 

[seefew]

@Ausdauersportler
I'm pretty sure I've take the correct rom
if I´ve understood correctly what I've read,
the K610M N15M-Q2 (HP # 785225-001) is suitable, but not
the K610M N15M-Q2-B-A1 (HP # 745325-001)
but anyway, the card was just lying around.
My mistake with the CH341A was that I'd deleted the chip, but on try to flash it flashrom returned the error message that the file to be written is too small for the chip and trying with -f does not change anything
The only thing i've not tryed until now is the CH341A in Win.
Now the Chip is empty and none of my Computers or Laptops will recognize the Card as a GPU even with shorten the SPI("1+8 Method")
Maybe i'll try it further soon
can you give me a link for @xanderon's Linux USB version please?

 

[herrdude]

@Ausdauersportler
I'm pretty sure I've take the correct rom
if I´ve understood correctly what I've read,
the K610M N15M-Q2 (HP # 785225-001) is suitable, but not
the K610M N15M-Q2-B-A1 (HP # 745325-001)
but anyway, the card was just lying around.
My mistake with the CH341A was that I'd deleted the chip, but on try to flash it flashrom returned the error message that the file to be written is too small for the chip and trying with -f does not change anything
The only thing i've not tryed until now is the CH341A in Win.
Now the Chip is empty and none of my Computers or Laptops will recognize the Card as a GPU even with shorten the SPI("1+8 Method")
Maybe i'll try it further soon
can you give me a link for @xanderon's Linux USB version please?

First page, first post.

 

[sOckhamSter]

Has anyone else has managed to get VDA Decoder to work in Catalina on an iMac 11,2 (mid-2010) with a K1100M? I'm asking cuz I'm tearing my hair out trying to get this working! So, at a basic level I have the whole dosdude Catalina installation working just great by following the various guides, it is literally just the iGPU I can't get working which I hope should allow me to watch Netflix/Prime in Safari.

My hardware: 21.5" iMac (mid-2010), 11,2. K1100M graphics card with patched VBIOS.

The process I'm following in brief, in this order:
- Boot from a USB configuration of dosdude1's Catalina patcher
- Install all of the post-install patches (including the legacy video. I've tried with and without, seems to install whatever I choose!)
- Fix the broken graphics with the "UNDOING DOSDUDE1 Video patches" process
- Fix the broken sleep issue and install IOSurface.kext
- Update AppleGVA.framework
- Fix the black screen issue with AppleGraphicsControl.kext

Checking in Hackintool and VDADecoderChecker always shows negative.

I have tried some of those latter steps in different orders to experiment, and I've also played with installing Lilu/WhateverGreen. I've even tried it out in OpenCore, but I figure if I can't get it working natively then I'm unlikely to be able to tweak it to work in OpenCore - I'd be very happy to be proved wrong on that!

I think the main issue might be to do with the iMac 11,2 being based on Clarkdale not Sandybridge which all the supplied kext files are targeting.

Has anyone managed to get this working with the same or similar hardware configuration, or are there some Clarkdale kexts knocking about somewhere? Thanks in advance for any information anyone can help here with.

 

[Ausdauersportler]

Has anyone else has managed to get VDA Decoder to work in Catalina on an iMac 11,2 (mid-2010) with a K1100M? I'm asking cuz I'm tearing my hair out trying to get this working! So, at a basic level I have the whole dosdude Catalina installation working just great by following the various guides, it is literally just the iGPU I can't get working which I hope should allow me to watch Netflix/Prime in Safari.

My hardware: 21.5" iMac (mid-2010), 11,2. K1100M graphics card with patched VBIOS.

The process I'm following in brief, in this order:
- Boot from a USB configuration of dosdude1's Catalina patcher
- Install all of the post-install patches (including the legacy video. I've tried with and without, seems to install whatever I choose!)
- Fix the broken graphics with the "UNDOING DOSDUDE1 Video patches" process
- Fix the broken sleep issue and install IOSurface.kext
- Update AppleGVA.framework
- Fix the black screen issue with AppleGraphicsControl.kext

Checking in Hackintool and VDADecoderChecker always shows negative.

I have tried some of those latter steps in different orders to experiment, and I've also played with installing Lilu/WhateverGreen. I've even tried it out in OpenCore, but I figure if I can't get it working natively then I'm unlikely to be able to tweak it to work in OpenCore - I'd be very happy to be proved wrong on that!

I think the main issue might be to do with the iMac 11,2 being based on Clarkdale not Sandybridge which all the supplied kext files are targeting.

Has anyone managed to get this working with the same or similar hardware configuration, or are there some Clarkdale kexts knocking about somewhere? Thanks in advance for any information anyone can help here with.

Have you ever read the instructions @highvoltage12v made in this particular post?
And why asking when you gave the answer yourself?

Another hint:
Some 2011 owner miss exactly the installations of these particular set of extensions. You are probably the first one to add them having non 2011 model. Added a not on post #1 for more clarity...

 

[sOckhamSter]

Have you ever read the instructions @highvoltage12v made in this particular post?
And why asking when you gave the answer yourself?

Yup, been through all 3 billion (ish) replies on this post and followed highvoltage12v's instructions to the letter in the hope it might work... and I'm asking because I've not necessarily given the answer, I'm just asking if I might be close to the answer with my suggestion, or if anyone else has this working via some method not yet discussed on this post (perhaps there's another post I haven't stumbled across in my multitude of searches specifically for Clarkdale issues?). If you personally don't know, no worries... someone else might? I'm still searching myself too and if I do find a solution I'll update here too for others to see.

Edit: just seen your updated note - yeah, I was adding the sandybridge stuff before I'd even checked that my CPU wasn't Sandybridge. Such a learning curve for most of these steps that the basics get forgotten easily Still on the hunt for a Clarkdale solution...

 

[Ausdauersportler]

Yup, been through all 3 billion (ish) replies on this post and followed highvoltage12v's instructions to the letter in the hope it might work... and I'm asking because I've not necessarily given the answer, I'm just asking if I might be close to the answer with my suggestion, or if anyone else has this working via some method not yet discussed on this post (perhaps there's another post I haven't stumbled across in my multitude of searches specifically for Clarkdale issues?). If you personally don't know, no worries... someone else might? I'm still searching myself too and if I do find a solution I'll update here too for others to see.

Another hint (copied from the post, not did not read well enough)
"I am creating a guide linked to the first page to show how to reinstall HD3000 sleep kext as well as bring back Airplay and intel Quicksync rendering. This guide is exclusive to 2011 iMacs Running Mojave or Catalina."

Wait, I have another:
You may also check the ark.intel.com page and other sources about CPUs having on chip H.264 support.

What comes next? Asking for HEVC and 4K H.264 support of your K1100M - you know the AMD cards have this and if you find enough extensions to install onto your iMac you will get it, too?

Okay, this was not fair...

 

[Ed Hartouni]

looking at the flash chatter, there does seem to be a difference between what xanderon posted and what I saw:


root@grml /lib/live/mount/medium/flash # ./nvflash_linux -6 Quadro_Beta1.2/K1100.rom

NVIDIA Firmware Update Utility (Version 5.414.0)
Simplified Version For OEM Only
Checking for matches between display adapter(s) and image(s)...

Adapter: Quadro K1100M (10DE,0FF6,103C,2256) H:--:NRM S:00,B:01,D:00,F:00

NOTE: Only IFR present:
NOTE: Skipping Board ID and Device ID checks.
NOTE: EEPROM does not contain board ID, skipping board ID check.

WARNING: Firmware image PCI Subsystem ID (1028.15CC)
does not match adapter PCI Subsystem ID (103C.2256).

Please press 'y' to confirm override of PCI Subsystem ID's: y
Overriding PCI subsystem ID mismatch
Current - Version:Unavailable (Invalid) ID:0000:0000:103C:2256

Replace with - Version DE.AD.00.BE.EF ID:10DE:0FF6:1028:15CC
Quadro K1100M by Nick[D]vB (Normal Board)

Update display adapter firmware?
Press 'y' to confirm (any other key to abort):
Identifying E

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?

EPROM...
EEPROM ID (EF,3012) : WBond W25X20A 2.7-3.6V 2048Kx1S, page
WARNING: Adapter does not have a preservation table,
unable to preserve board settings.
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

I got the AirPort card replacement for the one I wedged the connector off of on the last install...

Powering up the iMac after the replacement before putting the display back on, I watched the Diagnostic LEDs,
all 3 lights went on, indicating that the CPU and GPU were talking to each other. And the fans seemed to be running high, which I took as a further indication that I was in the ballpark.

GPU seems to be working, to first order...

Then I put the screen back on and got the same screen as upthread, after carefully checking all the cable connections to the screen.

Booting into the High Sierra system on my disk (another sign, I got the boot screen on holding the "Option" key down, so I suspect the flash worked) the system showed the progress bar, which stalled, then the system rebooted (indicated by the screen going black and the chime) to a black screen... so I don't know what is happening now.

I tried to boot into safe mode (holding the "Shift" key down) but after the chime it's just black screen... not sure how to implement the iFixit sequence without a screen (or system, though I don't know what I have).

 

[ZenSurfeur]

?!?!

 

[Tom.Tom]

Quick question (have searched through this thread to find the answer but maybe not deeply enough...):

When I switched from the previous version of the Catalina loader (the one from @herrdude's post linked to the 1st post) to the latest one based on OC 0.6.0 I noticed that the brightness change range is smaller in the latter. In the older loader I can change the brightness in the full range (from black screen to 100%) while in the latest one looks like something between 10% and 80%. This is the same for k610m and k2100m. Is it a known issue? Can I adjust it somewhere in the new loader?

Thanks in advance.

 

[rambo47]

My 2010 iMac was displaying some artifacts on the screen and I became concerned my graphics card was dying. After a restart and letting it sit for a day it seems the problem has sorted itself out, at least temporarily. This happened while I was looking to swap out a hard drive that has been making noises like boiling water. I am definitely putting in a SSD but I will hold off on the graphics card while I investigate my options.

It seems some upgrades are far less expensive than a replacement with the original card. The original is hard to source and costs close to $300 US! Seems I can get a much better card for $50-$70 instead and all I need to do is flash it. Most of the guides I've found are for 2011 models but it appears the 2010 is almost identical so I'm feeling pretty confident.

 

[Ausdauersportler]

Quick question (have searched through this thread to find the answer but maybe not deeply enough...):

When I switched from the previous version of the Catalina loader (the one from @herrdude's post linked to the 1st post) to the latest one based on OC 0.6.0 I noticed that the brightness change range is smaller in the latter. In the older loader I can change the brightness in the full range (from black screen to 100%) while in the latest one looks like something between 10% and 80%. This is the same for k610m and k2100m. Is it a known issue? Can I adjust it somewhere in the new loader?

Thanks in advance.

Try to replace the installed version with older or more recent versions of the AppleBacklightFixup.kext on the OC image. Cannot check with K1100M before posting, have no such card available. First post, again...

 

[Ed Hartouni]

I got the AirPort card replacement for the one I wedged the connector off of on the last install...

Powering up the iMac after the replacement before putting the display back on, I watched the Diagnostic LEDs,
all 3 lights went on, indicating that the CPU and GPU were talking to each other. And the fans seemed to be running high, which I took as a further indication that I was in the ballpark.

GPU seems to be working, to first order...

Then I put the screen back on and got the same screen as upthread, after carefully checking all the cable connections to the screen.

Booting into the High Sierra system on my disk (another sign, I got the boot screen on holding the "Option" key down, so I suspect the flash worked) the system showed the progress bar, which stalled, then the system rebooted (indicated by the screen going black and the chime) to a black screen... so I don't know what is happening now.

I tried to boot into safe mode (holding the "Shift" key down) but after the chime it's just black screen... not sure how to implement the iFixit sequence without a screen (or system, though I don't know what I have).

probably breaking more than I am fixing...

I decided to boot the system into the linux stick I made for flashing...
that worked, though the screen is the same.

I was able to communicate to the new GPU on the local screen. More disturbing, although the network showed an IP associated with the iMac, I couldn't ssh into the machine... so I wonder if the used AirPort card I got is working.

But, the screen was the same... perhaps some other cable is not properly connected, I broke a cable or a cable connection, etc... still not sure why the system doesn't boot.

Looks like I'll go back in and check the connections, and if I don't see any problems, replace the current GPU for the previous GPU and see if anything changes...

Ugh.

Sorry to share all this...
...maybe there should be a thread dedicated to the trials and tribulations of iMac 2011 GPU card upgrades... the first post referring to the first post of this thread, RTFM.