Got a tip for us?
Let us know
Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.
Thread '2011 iMac Graphics Card Upgrade' - Content history
Formatted Raw
-
Preamble (Last Updated 11/22/2020 - New format, Big Sur, K3000M)
This is not a plug and play solution!
You have probably found this thread because your iMac late 2009 to mid 2011 is having problems caused by the graphics card. It is well known that these graphic cards are problematic/defective. You will find websites that encourage "baking" the card. Without getting into the technicalities, it will work but this does not repair the graphics card. In fact, it only delays the problem. We have great news for you! You can install another graphics card that does not require much more effort. In addition, this will allow you to install more recent versions of MacOS. This thread has over 440 pages of useful information BUT the good news is all of that information has been summarized in this first post. It is HIGHLY recommended that you read through this post before asking questions. Then, reread the information. You will appreciate that the more experienced users cannot spoon-feed all new users. This distracts them from working on the files and tools that make all of this possible.
Before you post a question you may consider to add a signature to your account settings reflecting your machine type, graphics card, and possible even the problem you have. This signature sticks with every post you make and helps other to keep track and understand what is going on.
Enjoy!
This is the most important part of this process. The following information will help guide you in choosing your card. We have included the issues (loss of brightness control, loss of boot screen, loss of target display mode, etc.) to overcome when installing a non-stock card into a 2009-2011 iMac. When choosing your replacement graphics card, you must take under consideration: your budget, your comfort level with doing modifications, your ability to live with unresolved issues, your computing needs, etc. Unfortunately, this thread cannot help you source cards as there are two many variables involved. Read through this information carefully in order to choose the best card for your needs.
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).
- Only Nvidia Kepler cards or AMD Ellesmere/Polaris cards will work in these iMacs. No other GPU variant has MacOS driver support. Both get full graphics acceleration with all current MacOS versions including Big Sur.
- Please do not harass the BIOS developers to go faster, release a particular BIOS, etc. Please do not clog up the thread with useless posts asking if your specific card will get a new BIOS. Ask not what this thread can do for you, but what you can do for this thread. It takes several months of reverse engineering and testing before getting a new BIOS working. It took only six years for the first really working card here on this thread! If you would like to use a different card, consider yourself in unknown territory. Of course, let us know if it works! Chances are that Kepler based cards will run using the right (most likely Dell) BIOS but will exhibit the seven problems listed below.
- There are two type and sizes of cards: Smaller MXM-A cards and bigger MXM-B cards running stable only in the 27" models. While all cards will function in a 21.5" model, they are unstable due to their high power draw. @highvoltage12v tested a 770M here and had frequent Kernel Panics in macOS and BSoD's in Windows. Do not try it!
- For all Nvidia MXM B cards and the WX7100 you need the MXM-B heat sink from the 27" mid 2011 model. This is the only sink with three heat pipes capable to get the generated heat by using 75W out of the system unter load.
- You may face all kind of hardware problems after assembling your iMac again. There is an incomplete list of common (hardware) problems including the links to the original Apple iMac Technician Guides to trouble shoot such problems. Please understand that we cannot remotely repair or identify broken hardware. And there is no proof possible that hardware is broken. Do not ask for one. You may likely buy a dead used card. Check it before! This is not the "repair my iMac help desk thread".
Card BIOS link Boot Screen Brightness Control 21.5/27/MXM Heat Sink Mod perf Quadro K610M + ROM yes (natively) yes (OpenCore) yes/yes/A special install 35% Quadro K1100M + ROM yes (natively) yes (OpenCore) yes/yes/A no 65% Quadro K2100M + ROM yes (natively) yes (OpenCore) yes/yes/A no 100% Quadro K1000M * ROM yes (natively) no yes/yes/A no 35% Quadro K2000M * ROM yes (natively) no yes/yes/A no 65% Quadro K3000M ++ ROM yes (natively) yes (natively) no/yes/B yes, 2 pipe 100% Quadro K3100M ++ ROM yes (natively) yes (natively) no/yes/B yes, 3 pipe 130% Quadro K4100M ++ ROM yes (natively) yes (natively) no/yes/B yes, 3 pipe 200% Quadro K5000M ++ ROM yes (natively) yes (natively) no/yes/B yes, 3 pipe ? Quadro K5100M ++ ROM yes (natively) yes (natively) no/yes/B yes, 3 pipe 200% GTX 765M * ROM yes (natively) no no/yes/B yes, 3 pipe 110% GTX 770M * ROM yes (natively) no no/yes/B yes, 3 pipe 160% GTX 780M ++ ROM yes (natively) yes (natively) no/yes/B yes, 3 pipe 200% GTX 880M ++ ROM yes (natively) yes (natively) no/yes/B yes, 3 pipe 150% GTX 860M ++ ROM yes (natively) yes (natively) no/yes/B yes, 3 pipe 130% GTX 870M ++ ROM yes (natively) yes (natively) no/yes/B yes, 3 pipe ?
The perf column reflects the OpenGL performance relatively to the original HD6790M (Unigine Valley).
*
BIOS by @Nick [D]vB that currently enable boot screens on your iMac, better performance, and BootCamp support.
**
Only Nvidia Kepler based cards work in iMacs. The K3000M has been used with High Sierra by @Roman78. Using OpenCore all these cards can have a limited boot screen functionality, now.
+
BIOS by @Nick [D]vB, and the Wizzard @nikey22 that currently enable boot screens on your iMac. Using OpenCore with these cards offers right now native brightness control, target display mode, UEFI Windows 10, and more! To enable backlight in UEFI Windows 10, see this post by @internetzel.
++
BIOS by Wizzard @nikey22, and @stephle for the K5000M that currently enable boot screens and native brightness control on your iMac. To enable brightness controls in UEFI Windows 10, see this post and this more recent post. Only the audio support with UEFI Windows 10 would make OpenCore necessary.
These cards will run in a Late 2009 system, but all face (only there) another issue. After a PRAM reset the LCD remains black.
Fair warning:
There are K3100M, GTX780M (and possibly more type of) cards available on the grey market not working with the BIOS published and there are K3000M cards available not posting in some of the 2011 system. We cannot identify these in advance. Reason unknown. Other modifications like WiFi/BT or USB3 upgrades may interfere with the new GPU and destabilise the system. A "boot chime loop", i.e. non booting system is the final result.
Card BIOS link Boot Screen Brightness Control 21.5/27/MXM Heat Sink Mod perf AMD WX4130 +++ ROM yes (OpenCore) yes (natively) yes/yes/A special install 130% AMD WX4150 +++ ROM yes (OpenCore) yes (natively) yes/yes/A special install 130% AMD WX4170 +++ ROM yes (OpenCore) yes (natively) no/yes/B yes or no?, 3 pipe 150% AMD WX7100 +++ ROM yes (OpenCore) yes (natively) no/yes/B yes or no?, 3 pipe 230%
The perf column reflects the OpenGL performance relatively to the original HD6790M (Unigine Valley).
+++ These AMD Polaris cards are much more modern, but are difficult to source. Check the online offers carefully (the differences are explained below). With custom BIOS and OpenCore, these are very compatible and offer native brightness control, boot screens, UEFI Windows 10, and much more modern capabilities and future-proofing than the NVIDIA cards. They also allow for 4K H.264, and huge 4K HEVC decode/encode gains in production. There are still some problems to solve. Although SideCar will not work with these modern cards.
Using the GOP BIOS (links within the table above) you will have native brightness and and get an emulated boot selection only with OpenCore. OpenCore enables 4K H.264, and huge 4K HEVC decode/encode by using the iMacPro1,1 ID. This hack makes your iMac look alike a new machine and gives you similar features.
Using the EG BIOS version you will get a native Apple boot picker with an iMac firmware modification on an additional external display, only. These BIOS versions offer native brightness control, too. Without OpenCore you can have 4K H.264 with a modified AppleGVA.framework but no 4k HEVC. You can also use the same OpenCore setup as with the GOP BIOS versions and combine the best from both worlds. Here you will find new EG BIOS versions for the WX4xxxx line. Both solutions have their own advantages.
- AMD WX7100 (recognized as Radeon RX 580 in macOS)
It is important to identify the card. This card has been unpredictable. @Nick [D]vB has obviously a working card with number 109-C95847-00C_02. @Pascal Baillargeau has a card working with number 109-C95847-00D_02. However, other users have not been successful with the same exact models. For example, @Vego17 recently got the same card as @Nick [D]vB. But his card did not work in his iMac 2011 while it does run normally in a Dell Precision 7710 laptop. - AMD WX4170 (recognized as Radeon RX 560 in macOS)
Some come with a blank EEPROM and are missing a resistor. Working models with EEPROM are scarce. User @jborko did a write up HERE on his experience installing a WX4170. You can use the 4GB version of the latest WX4150 rom too (refer to the table at the beginning). - AMD WX4130/WX4150 (recognized as Radeon RX 460 or RX560 depending on used BIOS in macOS) - currently 09/10 Only
This card needs to have an EEPROM chip on board too. There are multiple versions of this card - only the "Dell" branded versions currently work. These WX 4130/4150 are not detected in every case by the 2011 iMacs for unknown reason, and therefore are currently not fully compatible. Even worse, some models are not detected in any iMac model from late 2009 to mid 2011. A few Dell versions will be recognized and run in 2011 models. There is currently no rule available to figure out in advance which model will run. Same situations as with the WX7100.
Q1: Is this easy? I need a quick fix for my iMac!
A: Not necessarily. This is not a plug and play solution! This "fix" is more of a "mod" to revive our iMacs. Depending on your scenario, it will require a full iMac disassembly, knowledge of BIOS flashing, dremel tools, heatsink modification, careful handling of logic board components, system administration at a higher level and some Unix or terminal command line awareness. With the used/grey market for many of these cards, other issues may pop up as well. Please inform yourself before undertaking this process.
Q2: My system boots up, but I don't have internal display, any display, or my GPU is not recognized correctly. What do I do?
A: Your MXM card is likely running an incompatible BIOS and will need to be flashed with the correct one. This can be done from within Windows or Linux using NVFlash, or with a CH341a programmer.
Q3: Flash VBIOS? How do I do that?
A: BIOS can be flashed in one of two ways: Either directly with a CH341a clip programmer or with the NVFLASH or AMDVBFLASH software in Windows or Linux. Only AMD cards and K610M, K1000M and K2100M cards can by used with the clip. Most NVIDIA cards have so called WSON BIOS packages. Experienced users may solder a different BIOS chip onto those cards to be used with a clip, too. You can use the flashrom software with the clip directly from the MacOS terminal following this installation guide.
User @xanderon created a pre-made USB that can flash Nvidia cards in the iMac with Linux over SSH. Many have found this the easiest method. There is an add-on to flash AMD cards using this method, too.
Additionally, user @jowaju created a simple Installer package that can be run on macOS Sierra (10.12) and higher that creates a 15GB Windows 7 Bootcamp partition with all the needed tools.
THIS external POST helps describes the flashing process. Others have found THIS POST useful.
Do a PRAM reset after flashing if you cannot boot into a known to work MacOS version!
Q4: OK, so I need to use the NVIDIA web drivers, right?
A: No - all cards outlined in this guide use the included NVIDIA drivers in macOS. No additional GPU drivers are needed.
Q5: Why aren’t you using Maxwell or Pascal cards in the iMac?
A: A lot of people here have tested Maxwell cards with their 2011 iMacs, and have had various issues from no internal display, no backlight on internal display and the card not hitting boost. Additionally, macOS Mojave (10.14) deprecated support for the NVIDIA Web Drivers which allowed the use of Maxwell and Pascal cards. For now, Kepler GPUs and the experimental Radeon cards seem to be our path forward.
Q6: Can I use a 4K display with these cards? The original card doesn't support 4K.
A: Yes! So far, the K1100M & GTX 770M have been tested firsthand and successfully provide 4K@60Hz output via mDP to DP adapter on a 4K display. Others should work just as well.
Q7: What paste is recommended to cover the VRAM/Components on the MXM card like Apple’s design?
A: For the GPU Die any thermal Paste like Thermal Grizzly’s Kryonaut paste is good for the Die. For onboard components, many recommend using K5 Pro Viscous paste instead of thermal pads, due to the unevenness of the heatsink, it’s also similar to Apple’s original Design. You can get it from the Bay or from the Book Store, too.
Q7: What kind of performance can I expect after installing one of these cards?
A: We are still aggregating GPU benchmarks. You can help by running UNIGINE VALLEY on your iMac at 1080P MEDIUM and submitting the OpenGL results. You can also view the results! Since the new GPU ofter native metal hardware support it is worth to measure this running the free GeekBench5 (metal), uploading, or reading the results.
Q8: Are there any internal modifications needed for an MXM-A swap?
A: For an MXM-A swap (the shorter/less power draw cards) there are no modifications that are needed for the heatsink on both the 21.5" and 27" model iMacs. The X-clamp still needs be removed from the back of the card and have the screw posts drilled or tapped out in order to fit the heatsink's screws. Separate the X-Clamp using a hair dryer before drilling or tapping - it is just glued to the board. Skipping this step can fry or damage your card. If you've cleaned your heatsink, be sure to re-apply thermal pads around the GPU VRAM to prevent contact with the bare metal of the heatsink. Use electrical tape to isolate card components from the sink! Watch closely after installing the card. Take a look at the attached pictures of this post!
Q9: Are there any additional internal modifications needed for an MXM-B swap?
A: The MXM-B cards only work on the 27" models due to power restrictions. There is one additional mod needed to make the MXM-B card fit. First you must grind down your heatsink in the area where one or two large coils sit, this way the card will sit flush with the heatsink. You must prepare the the X-clamp in the same way as described with MXM-A cards above. Take a look at the attached pictures of this post!
Some cards may work with the bigger MXM-B heat sinks with 2 copper pipes from the 2009 and 2010 models due to limited power draw. The WX4170 with a TPD of 50W is, the K3000M and K3100M may be such a candidate. The HD 5850M is listed with 40W-60W power draw.
If you have a 2 pipe heatsink that came with the lower end GPUs on these iMacs and want to use an MXM-B Card, you'll have to buy a 3 pipe heatsink to cool cards properly. You can get these on eBay.
Q10: After GPU change my system does not boot at all, what is wrong?
A: Most likely the installation of card on the heat sink caused a short, or the card is simply faulty, or the card has not been reseated in the slot properly, check all this out first. Any hardware issue has to be solved by yourself!
Q11: How to control the fans according to the internal temperatures?
A: We all know that none of the modifies BIOS versions for the Metal GPUs listed in the table above is able to provide the internal GPU temperature back correctly to by used by the iMacs internal Apple SMC software to control the (ODD) fan according to the GPU internal temperature. To address this issue we recommended strongly to use a free software called Macs Fan Control. But you can also try to solve this problem by using the ODD temp sensor.
Q12: What is video compared to graphics acceleration?
A: The fist term simply describes the fact that you can use GUI related operations like moving, resizing, closing an application or Finder window fast and smooth. This has been a serious issue with all patched installations of macOS versions on unsupported hardware. All "metal" cards listed above offer full graphics acceleration. Especially with Big Sur this has become more important since only "metal" enabled cards offer now the full graphics acceleration. The terminal video acceleration describes the hardware abilities of the GPU supported by the macOS. Only the new AMD GPUs offer 4K HEVC and 4K H.264 if installed in an iMac.
Q13: I want to help and experiment, what can I do?
A: First, read the full thread. Staying on top of the progress here is key! Currently we have released a series of BIOS versions for Nvidia GPU which do not need any hardware modifications, only some patched software. But there have been backlight mods created to be used with AMD and Nvidia BIOS versions which do not offer native backlight control. And of course every user may help sharing his knowledge to new users - but please stay on topic. This is not the thread of everything related to these old iMacs
This software is needed for Nvidia K610M, K1100M and K2100M to get native brightness control and for all AMD cards using the GOP or EFI BIOS getting a boot screen emulation and enabling 4k HEVC and 4K H.264 GPU acceleration and finally for all users of iMac 11,x systems to install and run Big Sur. It became a main part of this development, ignoring or denying does not help. You will not get the features described above without using OpenCore.
Benefits!
- Brightness control with K610M, K1100M and K2100M cards
- AMD Video acceleration 4K HEVC and 4K H.264
- Emulated boot picker for all systems using AMD cards!
- Big Sur for 27" Late 2009 and 21.5" and 27" Mid 2010 iMac models
Need to be done in advance?
- Install the lastest Apple firmware for your iMac. This can be done by doing a fresh High Sierra including all published Apple updates first on an internal disk before you can use the Catalina Loader or Mojave or Catalina or Big Sur.
- Before starting this use the RomTool and it's password (rom) from this site and backup your upgraded iMac EFI firmware and save it to an external storage device.
This High Sierra update will install a file called "Firmware.scap" to the (invisible) EFI partition of your internal iMac drive and during the next reboot(s) (of this disk) this EFI update will be applied. This takes some time in the dark (if your GPU BIOS has no working EFI boot screen to show the progress bar) , a loud beep may be heard and another reboot is coming.
What is OpenCore / Catalina Loader?
When we use the phrase Catalina Loader and OpenCore at the same time it is because the Catalina Loader is a piece of software using OpenCore.
Where to get it?
Just download the latest image and fitting OC EFI folder and install on an SD card or USB memory them drive, 1GB space will be sufficient. You will find a short documentation attached to the post. You just need to rename theconfig.plistfile in the EFI/OC folder on the SD card according to your GPU. Follow this docs attached at the post linked above.
More Information:
If you want to know what happens behind the curtain please read the original OpenCore post for more info. @herrdude provided an additional guide, another longer one by @Ausdauersportler and others named "Using Catalina Loader on an iMac" focussing on the special needs of 2011 models and special settings for AMD cards. All guides are worth reading before starting the installation.
More details about OpenCore on Legacy Apple hardware is available on this thread. The MacPro users basically explored the same things about Activate AMD hardware acceleration. Finally you may also study the OpenCore docs.
Using older MacOS versions (supported)
Currently we have no recent reports of users having a Kepler based Nvidia card installed with an older macOS versions than Sierra. According to this list the Nvidia drivers are part of macOS since 10.8.3. You might check this out on your own.
Installing MacOS Sierra (supported)
Supported MacOS version can be installed using the original Apple installer. To avoid the black screen issue install this package.
Installing MacOS High Sierra (supported)
Supported MacOS version can be installed using the original Apple installer. To avoid the black screen issue install this package.
Installing this last supported macOS version brings in the latest firmware. There will be unlikely ever new versions since High Sierra went out of Apple support these days.
Installing MacOS Mojave (unsupported)
The recommended method is to have High Sierra as your primary OS and install Mojave alongside on a separate partitions or APFS container partition. So if anything goes wrong, you can still boot back into High Sierra to fix issues. High Sierra offers a working recovery partition, too.
This is a two step installation. First you will use the @dosdude1 patcher and later install a package needed to address the hardware changes you made by changing the GPU.
1. You could preinstall Mojave before changing your GPU. Use dosdude1's Mojave patcher to do the install.
Important: While running the Post Install tool, make sure you deselect the Legacy Video Card patch option (since you will using a new, compatible metal graphics card).
2. GPU and machine related patches: (see next section common macOS problems)
Late 2009, Mid 2010: To avoid the black screen issue install this package or follow instructions this post.
Mid 2011: Install this package to avoid sleep problems, black screen etc. or follow this post.
Installing MacOS Catalina (unsupported)
The recommended method is to have High Sierra as your primary OS and install Mojave alongside on a separate partition. So if anything goes wrong, you can still boot back into High Sierra to fix issues.
This is a two step installation. First you will use the @dosdude1 patcher and later install a package needed to address the hardware changes you made by changing the GPU.
Important: Post-install patching has changed since Mojave.
Patching is now automated if your SMBIOS is detected to be an unsupported machine. Currently, only the 2011 iMacs have the "Legacy Video Card Patch" disabled by default. You will avoid this patch (since you will use a new, compatible metal graphics card) and will need to modify a plist file if you are using a 2009/2010 iMac with a Metal compatible video card or more easily while building the patcher, you can go to the "Options" menu and de-select "Auto-Apply Post-Install Patches" to avoid this.
Important: While running the Post Install tool, make sure you deselect the Legacy Video Card patch option (since you will using a new, compatible metal graphics card).
1. The process for Catalina is similar to Mojave as mentioned above. Use dosdude1's Catalina patcher to do the installation.
2. GPU and machine related patches:
Late 2009, Mid 2010: To avoid the black screen issue install this package or follow instructions this post.
Mid 2011: Install this package to avoid sleep problems, black screen etc. or follow this post.
See next section to manually fix this issue if you have accidentally installed this patch. Best option is reinstalling Catalina from the scratch!!
Installing MacOS Big Sur (Release 11.0.1 20B2029) (unsupported)
The recommended method is to have High Sierra as your primary OS and install Mojave alongside on a separate partition. So if anything goes wrong, you can still boot back into High Sierra to fix issues.
Having a Metal GPU makes your iMac Late 2009, Mid 2010, Mid 2011 Big Sur compatible. To make the package perfect and nearly fully compatible you could have installed an WiFi/BT upgrade, but it is not necessary to install and run Big Sur. The stock old Atheros WiFi card will be supported.
We managed to get all necessary patches for all iMac hardware to be included in the current state of the art Big Sur patcher (the @Barry K. Nathan micro patcher). There will be no manually installation of more extensions as with Mojave and Catalina, before. To understand the installation and patching process please follow the instructions provided on the Github download page step by step! The patcher will auto detect the installed GPU, although it cannot currently know if you are using an OC installation with your Kepler (K610M, K1100M or K2100M) card. In this case please use the--useOCwhen calling the patch.kext.sh script.
From version 0.5.3 on the detection of the GPU will happen automatically. You will not need any command line flag to use.
To avoid a kernel panic on boot of the Big Sur installer all users of the 2009 and 2010 iMac systems will have to use a special OpenCore based solution, to understanding the reason please read this post. This applies to all Kepler cards used, too. The most easy way will be to use the Catalina Loader provided here. There will be an update to the Catalina Loader using OC 0.6.3 including this patch, too. Check this post about the process of installation and normal boot of Big Sur using OpenCore.
Please keep in mind that the development is still ongoing and the developers on the thread cannot really support you with installation issues right now. You need MacOS and UNIX experience with the Terminal app and the command line to accomplish this task.
Notes:
- The stock WiFi and BT works properly patched, too. No HandOff and no Continuity, of course.
- AMD based systems offer 4K H.264 and 4K HEVC with Big Sur, again.
- Nvidia based systems lack currently still of iGPU based H.264 acceleration.
- Since all iMac 11,x models will need an OpenCore (OC) solution with Big Sur we have now only a few systems remaining working without OC, the iMac 12,2 using NVIDIA cards marked with a ++ in the table above. Due to this fact all systems using OC will have to use the Catalina Loader (CL) and the attached 0.6.3 (or later) EFI folders. These are preconfigured to inject all other extensions needed like Lilu, WhateverGreen, AppleBacklightFixup, PolarisBoost etc.
- All ++ card users with iMac11,x will need the special version of the AppleBacklighFixup.kext published here on the CL. It is the same link as in the table above. Please just replace the file on the CL in the EFI/OC/Kexts folder if and only if you experience any oddity with the backlight control.
After every MacOS update you will have to do the patching explained here to avoid common problems. Installing kernel extensions to the system is not an easy task. A complete installation guide to do this has been published (see link below with Q2).
Q1: I get a black or blank screen on boot, how to fix?
A: Sierra and later has been causing "black screen" issues for many folks. This is caused by a lack of kext initialization due to a lacking board-id in the AppleGraphicsControl.kext (short AGC). A patched AGC kext and a further explanation can be found HERE, thanks to @highvoltage12v. Please look and the next question and link to get the installation guide, needed. Using some Nvidia cards in late 2009 iMac causes extra pain. The internal LCD will come up only after installing the patched AGC and booting into the newly patched MacOS. The BIOS versions will need a fix to come around this additional problem.
Q2: Sleep is broken and QuickSync is not working on my iMac 2011 in Mojave and Catalina, how do I fix this?
A: Solution for Mojave and Catalina, the SandyBridge kexts are missing. Installing them fixes sleep, but causes extended boot times. @highvoltage12v has provided the needed patches containing the SandyBridge kexts in THIS POST which can be installed. You can also simply install this Catalina package or this Mojave package.
Q3: After installing Catalina on my Late 2009/2010 iMac my animations are broken/choppy, the Dock is grey and the menu bar isn't translucent. How do I fix this?
A: The dosude1 installer unfortunately automatically executes the "Legacy Video Card Patch" leaving Late 09/2010 MXM swapped users with broken/choppy animations. If you did install Catalina and would like to manually reinstall the stock Kexts and Frameworks, a guide has been written by @highvoltage12v to manually overwrite the patched files with stock files. Another fix is the reinstallation of Catalina with auto-patching disabled. It turns out to be the less error prone solution.
You may face all kind of hardware problems after assembling your iMac again. There is an incomplete list of common (hardware) problems including the links to the original Apple iMac Technician Guides to trouble shoot such problems.
Please understand that we cannot remotely repair or identify broken hardware. And there is no proof possible that hardware is broken. Do not ask for one. You may likely buy a dead used card. Check it before! This is not the "repair my iMac help desk thread".
Why do I find the plan at the very end of this post? Because the steps listed are described in more detail in the former sections. This plan is not complete and because we have five different iMac systems with different architectures, three different MacOS versions, nearly 20 graphics cards in mainly 5 flavours, we cannot make a simple single plan:
- choose a GPU, get the card (we do not comment on sellers)
- optional: get an SD card / USB this drive and prepare it with the Catalina Loader in advance if needed by the GPU
- upgrade your iMac boot rom firmware to the latest version (mandatory) by installing High Sierra on an internal disk including all recent Apple upgrades!
- using RomTool (password rom) dump your iMac firmware and store it externally (highly recommended)
- optional: get a CH341A clip programmer and install flashrom using brew on another Mac
- optional: apply the EG mod to your iMac firmware and restore the modified image using a CH341A clip
- optional: get an SD card / USB this drive and prepare it with the Linux flash utility, grab the most recent BIOS of your card of choice and copy it directly to the folder named flash on that drive
- get the most recent BIOS version following the links in the table above, flash the card using a clip programmer in advance or install the card and use the flash software tools (mandatory)
- relocate the ODD temperature sensor and install the card
- check the basic functionality with the latest supported OS which is High Sierra (highly recommended)
- install Macs Fan Control to and control the ODD fan according to the GPU heat sink temp sensor (mandatory)
- apply basic patches like the AGC if you experience a black screen (see above)
- optional: use the Catalina Loader (if needed by the card)
- make load test (UNIGINE valley and Geekbench5 metal) and submit results (see above)
- get used to the tools and patches, especially with OpenCore and Macs Fan Control
- move on to Mojave or Catalina using the @dosdude1 patcher (details see above)
- optional: apply sleep patches if using the 2011 iMac (Mojave and Catalina, only. see above)
- optional: install iGPU framework if using the 2011 iMac (Mojave and Catalina, only. see above)
Using a non Apple Card within an iMac creates these problems. Some have been solved with the published custom BIOS versions, others not. Especially the problem 7 has not been solved and needs a software solution.
- The loss of EFI boot screen;
- The loss of backlight control;
- You can only connect one external monitor to 27" iMacs;
- The loss of Target Disk Mode;
- The loss of Target Display Mode (TDM);
- The loss of running the built-in Apple Hardware Test (AHT);
- The loss of temperature sensors on the new GPU. But there is a solution!
You may use the OpenCore booter to add a boot screen feature to every card - even the Nvidia and AMD cards not listed here or known to have no BIOS support to show the original apple boot picker. There is a small delay between the chime (POST) and the initialization of the actual boot screen on the current NVIDIA modded BIOS. Most of the time (such as a quick reboot in macOS) the system boots too quickly for the EFI portion of the BIOS to initialize, making it appear that you may not have a "boot screen." All is working as intended if you can hold the "Option" key at startup and get a boot picker.
2. Native Brightness control is available for cards marked with + or ++ using a combination of custom BIOS and OpenCore.
For other cards, brightness control may be added in the future. Be aware that without brightness control, the iMac display runs at full brightness by default. For higher powered cards and 27" models, this can generate a lot of heat.
If you would like to "dim" your display using color dimming, many have used the app Brightness Slider, which is available on the App Store for free.
You can also use this app, which works better than most apps in the App Store, because it will dim the colors on the whole screen and it will display the built-in OSD, just like native brightness control.
Additionally, hardware level modifications using a DyingLight module or a Raspberry Pi have been used for brightness control. This software written by @passatgt can be run on a Pi for backlight control. Another hardware solution can be found here.
Nvidia cards marked with ++ with native brightness control may notice their displays are not hitting maximum brightness control Potential. A kext modified by @highvoltage12v can be found here to fix this issue.
Last, but not least: User @Lottosmp came up with a solution based on the former engineering.
3. Despite having 2 miniDisplayPort outputs, the 27" 2011 iMac will only output to one external display. There is currently no fix or workaround for this.
4. Target Disk Mode is available on all cards marked with a + or ++!
5. Target Display Mode (TDM) is available on for cards marked with + when using both custom BIOS and OpenCore. Target Display Mode is *only* stable under High Sierra and should not be used in later OS's.
6. Apple Hardware Test (AHT): There is currently no fix for running the internal service diagnostics. You may search the net for the ASD (Apple Service Diagnostic) package instead. For each system there is a different package. Download and install the package onto a SD card or a DVD, which will give you full functionality. A working download link may be hard to find. It is not open source.
7. GPU Temperature Monitoring is available on cards marked with a + or ++when using both custom VBIOS and OpenCore. A modified version of FakeSMC and GPUSensors is included with the OpenCore bundle to allow monitoring of GPU temps. But you still have to use some third party tool to control the fans. The GPU die temperature is not available and (probably for that reason) the Apple SMC still not running properly. Check the PDF attached to this post for details.
~~~~~~~~~~
Original Post from @MichaelDT June 14th, 2013.
I will be attempting to upgrade the MXM card in my 2011 21.5 iMac from the factory 6770m 512mb to a NVidia 675m 2GB. I choose this card because the chipset already has support from 10.8.3 onwards and affordability for an experiment. I am hoping that it will work without flashing like many of the other non MXM modern graphics cards (UEFI support) do in 64bit EFI Mac Pros ( I may loose the initial boot screen). But if all else fails I will attempt a flash. I will report back my findings when the card arrives (from Hong Kong). Wish me luck hopefully this will give those of us with the last modular iMac a path forward.