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Modèle A1312 / Mid-2011 / processeur 2.7 & 3.1 GHz Core i5 ou 3.4 GHz Core i7, ID iMac12,2

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880m GTX startup routine

Good afternoon iFixt community,

I have a question about the startup sequence of the iMac.

First let me explain what happened.

  1. I have a iMac with a ATI Radeon 4850 512MB MXM card, which works perfectly fine.
  2. I harvested a 880M from a laptop and flashed this with a BIOS version that support Apple.
  3. I replaced the card and got external display using mini DP.
  4. It can run games and the 880M is recongized and works.

But Internal display is not working with this new card. I put the ATI 4850 back and the internal works again. so the cable and display is fine. PSU is fine too.

Does somebody knows whats the diffrence between the ATI 4850 and 880M with startup, could it be that the 880M is not sending the right signals?

I measured the voltage on the 14 pin PSU connector all seems fine. Except pin 13 for enable backlight always is 0.00v to 1v.

If I solder a wire from a 3.3v source to the pin 13 will it work?

I think maybe the 880M doesn’t send a signal for enable backlight and startup video using the LVDS connector I have no clue or if the display and video card together draw to much current together? But external works, but external is of course is different power source for its display.

Does someone have a clue??

My last resort is soldering wires to generate/ force signals. But I have read in other iMac’s that people did this and killed the logic board because sometimes signals only need to be a second there.

Update:

Dan fixed my issue.

For anyone else who see this or want the info .. in the link Dan posted

They said it doesn't work in high sierra

But here it does, also I didn't lose boot screen it's there using a vbios from nickey on macrumors I found it a while back.

Catalina and others didnt try.

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Your system came with either a AMD Radeon HD 6770M or Radeon HD 6970M. And offered 512 MB GDDR5 (Radeon HD 6770M) 1 or 2 GB GDDR5 (Radeon HD 6970M) of Video RAM.

par

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I haven’t done this my self so I can’t tell you if this will fix your issue or not. Forcing an NVIDEA into a iMac is very iffy! Apple only offered one driver so you’ll be running in compatibility mode! I don’t see Apple supporting NVIDEA in Big Sur if that was your direction, I think Catalina is it for the driver.

Successful iMac Upgrade to GTX 880M

To make a non-apple provided NVIDEA graphics card work in macOS Sierra you need to do the following…

Start the computer in safe mode by holding shift.

Get your BoardID by running this command in terminal

echo "<result>$(ioreg -rd1 -c IOPlatformExpertDevice | awk -F'["|"]' '/board-id/{print $4}')</result>"

Open the AppleGraphicsControl Kext using this command

sudo nano /System/Library/Extensions/AppleGraphicsControl.kext/Contents/PlugIns/AppleGraphicsDevicePolicy.kext/Contents/Info.plist

Use the arrow keys to go down until you see <key>ConfigMap</key> followed by a bunch of keys and strings.

LOOK FOR YOUR BOARD ID…

IF IT IS LISTED: Change the string to <string>none</string>

IF IT IS NOT LISTED: Add it in the same format as the ones listed.

Save the file by pressing Ctrl+O, then enter.

Exit by pressing Ctrl+X

Rebuild the kernel cache using the following two commands:

sudo kextcache -system-prelinked-kernel

AND

sudo kextcache -system-caches

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4 commentaires:

Dan ur the man, I already found this solution a way back but I didnt suspect this would work.

I just verified it this works!!

Thank you

Still I don't understand the apple sysrem

I suspected a bios or not bootable mac osx

This means I would always need a remote login or external display to do this modification

Still can't believe this solved it..

par

A good way to think this is like a shoe cobbler... You walk into the shop with your shoes on clearly he can't fix your shoe while you are in them ;-}

The reason you get into trouble is the system has two graphics services the one within the Intel chip and the AMD (NVIDEA here) GPU. The systems EFI (BIOS) only has the Intel driver and pointer to your OS kext file which points to the discreet driver for the GPU board. Here the kext is set for the AMD board driver.

Without the proper firmware on your NVIDEA board your screen won't be active until the NVIDEA driver is loaded. This is why you have a black screen and can't access any of the startup keys to enter into diagnostics D as an example.

par

Dan can u explain this a bit more in terms with.

Gpu 1 ati 4850

Gpu 2 nvidia 880m

I'm confused now

This was a pretty nasty issue.

Because I suspect or though screen was bad..

Cause all voltage was right I found the 12v towards screen stuck in the mosfet drain was 0_1v but screen was not attached cause if attached I can't measure.

So I changed back old gpu and then I noticed all worked still.

Also I'm afraid of this solution cause will a software update modify this file again and the same issue appears back?

Is it also strange that the intial boot sequence doesn't have a basic for loading and showing the apple image. Cause the edit is a system file of the operating system I guess.

It makes

par

The original MXM GPU that your system had was either a AMD Radeon HD 6770M or Radeon HD 6970M. (ATI is the company AMD bought). The ATI Radeon HD 4850 board you have in this system is from either a 24" Early 2009 or a 27" Late 2009. Its not the original MXM GPU this system had.

The driver is either the AMD or the NVIDEA each one is programed for their own GPU boards. You can't substitute one for the other. But you forgot the 3rd graphics source in this dialog! The one within the Intel CPU chip! So its the Intel then the AMD or its Intel then the NVIDEA.

If the system is expecting the AMD per the kext then thats what is loaded, not the NVIDEA which you installed! The whole issue with the external display has to do with the fact you are using the Intel graphics engine not the GPU as the way the external port is wired by default is the CPU's graphics until the driver is loaded (which in this case wasn't)

Yes, the last issue was the custom firmware within the AMD or the NVIDEA MXM board is also a factor if not programed correctly can drive you bonkers!

The Bottom-Line: You are forcing a GPU board Apple did not support in this system. And as Apple doesn't use commodity products without tweaking them (HDD's & GPU boards) using unmodified devices can lead to incomplete solutions and maybe short lived. Here you are using a GPU board to gain Metal support so you can run an unsupported OS Mojave or newer. Leveraging an old GPU driver, to add to that the driver is not being maintained. Apple tends to remove drivers on the older hardware around 10 years out so the NVIDEA driver is not expected to be available in newer OS releases.

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Hello Dan.

Sorry for my English.

I want to order GTX 880M and my HD 6970M is dead two card I replaced and work maxim 1 year.

I found information in the internet the GTX 880 from Dell Alienware ca be work?? Now it's Sierra osx

Can you explain is it work or not in 2021?

Thank you

Best regards

Roman

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I just tried to install a GTX 880m apparently its a ex Dell card.

My problem is the iMac will not even power on with the internal lcd connected.

Led1 will stay lit and do nothing, disconnecting the LVDS cable the iMac boots fine to a external monitor via mini dv cable.

It the 880m flashed fine via terminal, i tried re-flashing but makes no difference.

If i hot swap the LVDS cable then reboot i can get the internal lcd to work however if i shut down and power back on i get the boot chime loop over and over.

My guess is the card just isn't compatible.

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kingbacana sera éternellement reconnaissant.
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