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Thread '2011 iMac Graphics Card Upgrade' - Content history

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  • iMac Late 2009 to Mid 2011 graphics card upgrade (Last Updated 06/02/2021

    This is not a plug and play solution! You need extended macOS / Unix system administration knowledge, the ability to run programs from the Terminal app and some manual skills to assemble your iMac again. If you have not done this before, get some local help in advance and make a complete plan and make notes while reading through this page and thread!

    It is HIGHLY recommended that you read through this post before asking questions. Then, reread the information.

    Before you post a question please 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.

    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. It takes several months of reverse engineering and testing before getting a new BIOS working.

    There is no simple best card: Your budget, your comfort level with doing modifications, your ability to live with unresolved issues, your computing needs, the local market, your iMac, etc. will determine the card to be used.

    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.
    1. The modified (video) BIOS version require an Intel i3 CPU or better.
    2. Only Nvidia Kepler GK104, GK106, GK107 cards or AMD Baffin, Ellesmere, Polaris20, Polaris21 cards will work in these iMacs with macOS including Big Sur. No other GPU variant has macOS driver support.
    3. There are smaller MXM-A cards and bigger MXM-B cards running stable only in the 27" models. While all cards may function in a 21.5" model, the big ones are unstable due to their high power draw. Do not try it!
    4. All NVIDIA MXM B cards, the WX7100, and the RX480 need the big three copper pipe MXM-B heat sink from the 27" mid 2011 model to get the generated heat out of the system under load. No exception!
    5. Tests with iMac10,1 21.5" Late 2009 and iMac9,1 24" Mid 2009 with a new GPU have been made. External displays worked, internal LCD screen did not unless you buy a special driver board and connect the internal screen with the external miniDP port (and make it an external one). Check carefully which driver board you might need. Some other cards may work with the stock BIOS showing all the seven problems... work is ongoing.

    Most of these cards hit the street before 2012 and are considered old cards.

    Known issues or problems:
    1. Dead cards: Some of the a 7-10 year old used Nvidia on the market may be already (half) dead. Some sellers offer cards with new BIOS - but to small - chips soldered on. Ignore those offers.
    2. iMac 2011: Some NVIDIA GPU may not run well in your 27 Mid 2011 iMac. We have reports of 880M, K3000M, K3100M, K4100M which all run only without the internal LCD connected. As soon as you connect the LCD the system refuses to boot or ends up in boot chime loop. Reason unknown.
    3. Memory type: NVIDIA cards can have different memory types (Hynix AFR, Hynix BFR, Elpida, Samsung). Take a look at the links within the tables to find your fitting BIOS. For some cards - although listed below - we may not have the correct memory versions prepared.
    4. Black Screen: After complete installation of the iMac the internal LCD can stay black, only three status LED light up. This is the black screen software issue. Normally you can get around it (temporarily) by pressing alt/option on boot. Late 2009 system you will face (only there) a more severe variant. After a PRAM reset the LCD gets and remains black. To fix this for all iMacs a kernel extension needs to be patched at best in advance. Only after booting into this patched macOS the screen will come back. Use this package installer to achieve this with all ++ cards on all systems up to macOS Catalina. Do not use this package on Big Sur. important: OpenCore (OCLP) with agdpmod=vit9696 in the boot-args fires up the LCD after a PRAM reset or GPU change, too.
    5. Color depth problem: Happens on after boot - just sent the system once to sleep or change resolution. This solution or this opencore based solution will cure the problem.
    6. Brighness level: Solution is linked here for all ++ cards and described by @nikey22 on each of his posts, again.
    7. Brightness control with OpenCore: All + cards need OCLP or CL to enable brightness control!
    8. BIG MXM-B cards need MXM-B heat sinks to transport the heat way. Do not use small MXM-A sinks unless you want to kill your card.

    CardBIOS linksBoot ScreenBrightness Control21.5/27/MXMHeat Sink ModOGLMET
    Quadro K500Mnonoyes/yes/An/an/a
    Quadro K510Mnonoyes/yes/An/an/a
    Quadro K610M +ROMyes (natively)yes (issue 7 above)yes/yes/Aspecial install505n/a
    Quadro K1100M +ROMROM1yes (natively)yes (issue 7 above)yes/yes/Ano907n/a
    Quadro K2100M +ROMROM1yes (natively)yes (issue 7 above)yes/yes/Ano1229n/a
    Quadro K1000M +ROMoldROMyes (natively)yes (issue 7 above)yes/yes/Ano903n/a
    Quadro K2000M +ROMoldROMyes (natively)yes (issue 6 above)yes/yes/Ano797n/a
    Quadro K3000M ++ROMROM1yes (natively)yes (issue 6 above)no/yes/Byes, BIG 2 pipe116415
    Quadro K4000M ++ROMyes (natively)yes (issue 6 above)no/yes/Byes, 3 pipe1680n/a
    Quadro K3100M ++ROMROM1ROM2yes (natively)yes (issue 6 above)no/yes/Byes, 3 pipe177921
    Quadro K4100M ++ROMyes (natively)yes (issue 6 above)no/yes/Byes, 3 pipe246532
    Quadro K5000M ++ROMROM1yes (natively)yes (issue 6 above)no/yes/Byes, 3 pipe203829
    Quadro K5100M ++ROMyes (natively)yes (issue 6 above)no/yes/Byes, 3 pipe2404n/a
    GTX 680M ++ROMyes (natively)yes (issue 6 above)no/yes/Byes, 3 pipen/an/a
    GTX 765M +ROMyes (natively)yes (issue 7 above)no/yes/Byes, 3 pipe1428n/a
    GTX 770M +ROMyes (natively)yes (issue 7 above)no/yes/Byes, 3 pipe2140n/a
    GTX 780M +ROMyes (nativelyyes (issue 7 above)no/yes/Byes, 3 pipe264241
    GTX 780M ++ROMyes (natively)yes (issue 7 above)no/yes/Byes, 3 pipe264241
    GTX 880M ++ROMyes (natively)yes (issue 7 above)no/yes/Byes, 3 pipe2700n/a
    GTX 860M ++ROMyes (natively)yes (issue 7 above)no/yes/Byes, 3 pipe161634
    GTX 870M ++ROMyes (natively)yes (issue 7 above)no/yes/Byes, 3 pipe232640

    OGL column: OpenGL performance based on the Unigine Valley score from this table. T
    MET column: Metal performance based on MetalBench score from the table.

    *
    BIOS by @Nick [D]vB that currently enable boot screens on your iMac.

    +
    BIOS by @Nick [D]vB, @nikey22, @Santa's Little Helper that currently enable boot screens on your iMac. Using OpenCore (through OLCP or Catalina Loader for High Sierra and Sierra) these cards offers right now native brightness control, target display mode, support of UEFI Windows 10, and more!

    ++
    BIOS by @nikey22, and @stephle for the K3000M/K5000M that currently enable boot screens, native brightness control, target display mode.

    Notes:
    1. Most if not all of these cards have a WSON type BIOS chip which cannot be programmed using a clip. You need nvflash with Windows or Linux. Take a look at the FAQ about flashing cards.
    2. Audio support with UEFI Windows 10 would make OpenCore for any listed card necessary!
    3. To enable brightness controls in UEFI Windows 10, see this post and this more recent post.
    4. Target Dispay mode works only with High Sierra an older!

    These cards have been introduced 2016 and later and are considered as new cards. The GPU is more power efficient compared to Nvidia Kepler and have by far higher metal performance.

    Known problems:
    1. General: Some AMD cards will not POST (Power On Self Test) in the Mid 2011. This happened with some WX7100 models, all RX480, some HP AMD cards. A solution for the HP 4150 has been published.
    2. AMD WX7100
      It is important to identify the card. @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.
    3. AMD WX4170
      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.
    4. AMD WX4130/WX4150
      There are multiple versions of this card - only the green "Dell" branded versions currently work in every model. The HP WX4150 needs this mod for 2011 iMac12,2 27 inch models.
    5. AMD RX480 Works only in Late 2009 27 and Mid 2010 27 systems!

    CardBIOS linkBoot ScreenBrightness Control21.5/27/MXMHeat Sink ModOGLMET
    AMD WX4130 +++ROMyes (OpenCore)yes (natively)yes/yes/Aspecial install180553
    AMD WX4150 +++ROMyes (OpenCore)yes (natively)yes/yes/Aspecial install180562
    AMD WX4170 +++ROMyes (OpenCore)yes (natively)no/yes/Byes or no?, 3 pipe215673
    AMD RX480 +++ROMyes (OpenCore)yes (natively)no/yes/Byes or no?, 3 pipe2800150
    AMD WX7100 +++ROMyes (OpenCore)yes (natively)no/yes/Byes or no?, 3 pipe2949160

    OGL column: OpenGL performance based on the Unigine Valley score from this table. T
    MET column: Metal performance based on MetalBench score from the table.

    +++ These AMD cards are much more modern, but are difficult to source. Check the online offers carefully (the differences are explained above). The cards are be supported natively with Sierra and later. Latest known working macOS version is currently Big Sur.

    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. Does not work with Sierra when using OpenCore!

    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. You can also use the same OpenCore setup as with the GOP BIOS versions to enable 4K H.264/HEVC. Here you will find new EG BIOS versions for the WX4xxx line. Both solutions have their own advantages.

    Can be flashed using a clip or amdvbflash with Linux or Windows or EFI. Take a look at the FAQ about flashing cards.

    Here a list of related external projects:
    • MXM carrier board with PCI extender to plug in an eGPU into 27 Late 2009-2011 iMacs
    This is a short list of enhancements worth to be realised IMHO:
    • add (Atheros and BCM94xxx) WiFi drivers to Linux Flash utility
    • modify iMac Late 2009 i-series firmware to avoid total eclipse (black screen) (solved with OpenCore with agdpmod=vit9696)
    For those about to solder or code, we salute you!

    Here the most frustrating (hardware) problems:
    • why do some AMD MXM cards still not POST in the iMac12,2 2011 system (RX480/WX7100)
    • how to solder a BIOS chip on the WX4170 cards without one (in progress)

    A: Not necessarily. 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. Please make a plan before jumping into this!
    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. Some HP cards do not contain any BIOS and will not show up in the system until flashed (sometimes only possible with a CH341A clip!)
    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 most AMD cards and K610M, K1000M and K2100M cards can be used with the clip. All other 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.

    AMD flash software and NVIDIA flash software is only available on Windows and Linux.

    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. SSH clients are available for iPad, iPhone and other tablet devices, too. The latest version is available here.

    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!
    A: No - all cards outlined in this guide use the included NVIDIA drivers in macOS. No additional GPU drivers are needed.
    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 (new) AMD cards seem to be our path forward.
    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.
    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. How to apply the paste, watch this video!
    A: We are still aggregating GPU benchmarks. There is a special section on this page and we added to the GPU tables a relative (to the old flagship HD6970) performance column only based on the the OpenGL benchmark.
    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 new 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! In case you had a ATI card using a small Apple X-bracket (all MXM-A cards, 4850 and 5850) just reuse this bracket!! It fit's perfectly with all MXM-A replacement cards!
    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. In case you had a ATI card using a small Apple X-bracket (all MXM-A cards, 4850 and 5850) just reuse this bracket!! It fit's perfectly with all replacement cards except the RX480 and WX7100!
    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.
    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!
    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.
    A: The first 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 term 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. If you want to know more about the possibilities AMD cards offer watch some of the videos collected here.
    A: This issue has been described by the author of the BIOS on every publishing post. So it is a BIOS issue which can be solved by just sending your iMac once to sleep and on wake up the graphics driver will re-initialise and the color mapping will be correct or you simply use this little app made by @passatgt and follow his instructions.
    A: Take a look at this post...this is not a plug and play task.
    A: This feature is only supported until High Sierra on the iMac. To use it you need a working High Sierra partition/container on your boot disk. Apple dropped TDM support for M1 systems. You will not be able to use an iMac as an external display for these new 2020+ machines. For older Intel based systems until 2019 you will need the Apple Thunderbolt 2 (Mini DisplayPort female plug type) to Thunderbolt 3 converter cable (USB-C plug type).
    A: First, read the recent part of thread and this post on a regular base. Staying on top of the progress here is key! And of course every user may help sharing his knowledge to new users - but please stay on topic!

    What is OpenCore?

    OpenCore (OC) is software to enable some features and provide necessary data before an unsupported or supported macOS boots. This way we can solve sleep/wake and black screen issues without modifying the installation itself.

    Important advices: DO NOT IGNORE!
    • AMD GPU users should install the OpenCore created with OCLP on the Catalina Loader or internal disk. If the configuration fails you end up without a non booting system and to force a boot of an external UBS device to reinstall you have to change the boot selection - which cannot be done without an EFI Boot picker acting on alt/option on boot. The Catalina Loader cannot be made the standard boot object from Big Sur. You need Catalina or older to do so. Have a small partition with High Sierra for that reason! If things break you will have to pull the disk out of the iMac to force boot of an external device. This can be avoided by having the OC on the CL on an SD card or USB thumb drive which can be pulled out of the system.
    • Users of UEFI Windows installation should check the contents of the internal EFI folder. You cannot install OC and MICROSOFT sub folder in EFI as the iMac firmware will only be able to manage a single boot loader per EFI partition. In this case use the second internal disk for OC (if existing) or an USB device.
    • Owners of NVIDIA cards with an EFI Boot screen should install the EFI folder directly to the EFI partition of the internal disk (process described in the OCLP docs) unless Windows exists still there...
    Why using OC!
    1. Native and unpatched installation of Mojave, Catalina and Big Sur with OpenCore Legacy Patcher (OCLP)
    2. Brightness control with K610M, K1100M, K2100M, GTX765M, GTX770M, (GTX780M) cards
    3. Emulated boot picker for all systems using AMD cards!
    4. WINDOWS 10 UEFI installations on Mid 2011 sound patch
    5. AMD Video acceleration 4K HEVC and 4K H.264
    6. OTA (over the air) on Big Sur, Mojave, and Catalina
    7. AMD DRM (HW support) for Netflix (not in Safari), AppleTV, Amazon Prime etc. streaming
    8. solves black screen issue with all NVIDIA GPU (add agdpmod=vit9696 to boot-args)
    Where to get it and how to use?

    Download: OpenCore Legacy Patcher

    For more details check the section below: Upgrade your (mac)OS on the metal capable iMac

    More Information:

    Thread: macOS 11 Big Sur on Unsupported Macs
    Thread: OpenCore on Legacy Apple Hardware (focusing on MacPro, but also a lot of general instructions)
    Thread: Activate AMD hardware acceleration

    Videos: How to maintain OpenCore
    Full documentation: Dortania OpenCore.

    History:

    Catalina Loader (CL) is another software allowing OC to be installed and maintained more easily than on hidden EFI partitions

    Download (for Sierra and High Sierra): Catalina Loader image and original OC version
    Post: The original OpenCore post on this thread
    Guide: Guide by @Herrdude
    Guide: Using Catalina Loader on an iMac

    Follow this link to install Windows using the UEFI method or search the net for more ways to achieve this. You will need OpenCore to enable the sound on 2011 systems using this method! To avoid blue screen issues on the iMac12,x read this doc.

    According to this list the (Kepler) Nvidia drivers are part of macOS since 10.8.3. You might check this out on your own. At least on recent successful upgrade of an iMac 12,2 with macOS 10.10 can be reported here.
    According to this GPU buyers guide the new AMD will be supported with macOS Sierra and later.

    Supported MacOS version can be installed using the original Apple installer. To avoid the black screen issue install this package.

    Supported MacOS version can be installed using the original Apple installer. To avoid the black screen issue with NVIDIA cards install this package.

    Installing this last supported macOS version brings in the latest firmware. There will be unlikely ever new firmware versions since High Sierra went out of Apple support these days.

    Using an AMD GPU you need to install OpenCore using the latest OCLP. This way you can use all the superior funtionality of the AMD GPU and avoid any possible problems like sleep/wake issues!

    The recommended method is to have High Sierra as your primary OS and install Mojave/Catalina/Big Sur alongside on a separate partition. So if anything goes wrong, you can still boot back into High Sierra to fix issues. Make sure it is the partition the iMac boots in after a PRAM reset automatically!

    Having a Metal GPU makes your iMac Late 2009, Mid 2010, Mid 2011 fully compatible, again.

    You have a single patcher option for all new macOS versions based on integration work of @Ausdauersportler into the tool provided by @khronokernel and @dhinakg! It can be used to install macOS Big Sur as well as Mojave and Catalina. After installing OpenCore your system will be qualified to run the stock installer programs provided by Apple.
    • OCLP (this package offers a recent OpenCore package and is in fact an Big Sur installer at the same time)
    We recommend all new users to use OCLP and I ask all current iMac micropatcher users to migrate to OCLP with the next full installer. This is the future proof solution. Do not use other patchers! First read the documentation linked on the download page.

    The OCLP patcher app will auto detect your system, BT, WiFi card and GPU. Carefully check in Build OpenCore step if everything has been detected properly.

    If you plan to use/install High Sierra or Mojave or Catalina using OCLP follow the manual approach described below.

    If you plan to use/install High Sierra or Mojave or Catalina using OCLP enter the Patcher Settings and
    1. set SMBIOS Mode->moderate
    2. disable Securebootmodel by SBM->False
    3. disable SIP with setting SIP->False
    This is currently unsupported by the OCLP dev team but it works like a charm. You can set everything according to your needs and even generate configs for different systems by bypassing the auto detection. Start with changing the model.

    After Mojave/High Sierra installation you can fix the PreBoot/Recovery of both these macOS versions and reset SBM and SIP to true. This way you can use OCLP to boot into High Sierra, too. It enables the superior 4K HEVC and 4K H.264 as it contains the brightness control patches. No need to change a Catalina installation!

    Reboot, press alt/option and select the OpenCore on boot. Make it default by pressing CRTL.

    Known Issues with Big Sur 11.3 and newer:
    • the kernel sometimes stops working during the installation process due to a race condition. You can force a reboot and proceed with the installation normally. This happens on all iMac11,x and iMac12,x systems and is not an patcher issue - this is an Apple bug. Stay on 11.2.3 if your are not willing to experiment.
    • using Big Sur and High Sierra on the same machine can corrupt the Big Sur preboot volume and prevent it from booting properly. Take a look and this post for a solution. You will disable the mount of the Big Sur volumes when starting High Sierra.
    Known issues OCLP (version 0.1.5):
    • none
    Notes:
    1. Do not update a @dosdude1 patched installation of Mojave or Catalina, please backup user data, make a clean installation, restore user data.
    2. The stock Atheros WiFi and old BT works with both options, too. No HandOff and no Continuity, of course.
    3. AMD based systems offer 4K H.264 and 4K HEVC with Big Sur, again. DRM is working again and so Apple TV will show movies online, Netflix (currently not in Safari), Amazon Prime and others should work, too.
    4. Nvidia based systems lack currently still of iGPU based H.264 acceleration. HW DRM has never worked. There is legacy video support coming back with. Possibly this will solve the iGPU problem on 2011 systems.
    5. OCLP can be used without any patching and if offers SIP, File Fault and most importantly OTA upgrades. No other tool can offer this without additional complications.
    6. AirPlay will work with AMD dGPU and Mojave and Catalina using the original Atheros WiFI card. Big Sur needs a Broadcom upgrade. No tests made with NVIDIA dGPU.

    This is a legacy patching instruction. We strongly recommend to use OCLP to install any macOS Mojave and later. This section is only important for users of Mid 2011 systems with an NVIDIA card needing Intel QuickSync (H.264 encoding) to work.

    AMD users will use the AMD GPU superior H.264 encoding and do not need Intel QuickSync. So an AMD user will never need to install using this method and have to use OCLP!

    The recommended method is to have High Sierra as your primary OS and install Mojave/Catalina 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.

    Important: Post-install patching has changed since Mojave.
    Patching is 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).

    1a. The process for Catalina is similar to Mojave as mentioned above. Use dosdude1's Catalina patcher to do the installation.

    1b. Getting the latest Catalina installer is broken with the latest @dosdude1 patcher. You need the gibMacOS utility to download the latest version and construct it from the several download files. Follow the instructions coming with the tool. Then in can be installed using the latest @dosdude1 patcher. This method works for all recent macOS versions!

    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!!

    Status 05/07/2021:
    • DRM is known to work and you can watch Apple TV and Netflix on your iMac with AMD GPU, only.
    • use gibMacOS (download code on green button and read the online docs) to download the latest and last full Catalina installer (19H05). A complete installation recipe has been published here...
    • (using NVIDIA GPU) H.264 iGPU acceleration is still working on the 2011 models
    • (having a 2011 system) installing @dosdude1 and later sleep patches found on post #1
    • (having a 2009 and 2010 system) disable auto install patches in advance otherwise the legacy video patch make the fresh installation unusable
    • security upgrades using the @jackluke OTAfix trick (latest Beta security upgrade is 19H505)

    After every MacOS update only when using a @dosdude1 patcher you will have to do the patching explained here to avoid common problems, again. 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). You can do this using the provided installer packages, using some tools or using the terminal and command line.

    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 @dosdude1 installer 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 more easy fix is the reinstallation of Catalina with auto-patching disabled.

    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.

    Some other possible modifications as USB3 or WiFi/BT 4.x replacements may interfere with a new GPU.

    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!

    1. OpenGL

    OpenGL performance can be measured using the free Unigine Valley. Use these standard settings as resolution of 1920x1080, quality Medium, stereo 3D disabled, Anti-aliasing Off to compare results.

    2. Metal

    Metal has been introduced in 2012 hardware (HD4000 and NVidia GPU). Use GeekBench5 Metal or the more meaningful MetalBench software (Catalina and later).

    Table of Benchmark Software and upload and result forms

    SoftwareDownloadUpload FormResult form
    Unigine Valley OpenGLdownload Valley from hereupload results hereview results here
    Geekbench5 Metaldownload GeekBench5 hereupload results hereview results here
    MetalBench Metaldownload Metalbench hereupload results hereview results here

    Apple M1 (MacBookAir) Unigine Valley 57.5 FPS, 2405 Score

    Most - if not all - of these problems have been solved with the published BIOS versions.

    Using a non Apple video card within an iMac will create these seven problems.
    1. The loss of EFI boot screen;
    2. The loss of backlight control;
    3. You can only connect one external monitor to 27" iMacs;
    4. The loss of Target Disk Mode;
    5. The loss of Target Display Mode (TDM); (works only with High Sierra and before)
    6. The loss of running the built-in Apple Hardware Test (AHT);
    7. The loss of temperature sensors on the new GPU. But there is a hardware solution!
    1. Boot Screens are now available on all listed cards using custom VBIOS and/or OpenCore

    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. It has been added to all installer packages and the Bit Sur patcher.

    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. This shows the temps, but does not control the fans!
    Use Macs Fan Control to control the ODD fan. Check the PDF attached to this post for details. The best solution as of today is to relocate the ODD sensor as described in this solution! The ODD sensor will drive the fan up using the Apple SMC software.


    ~~~~~~~~~~

    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.
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