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Author Topic: iMac 2011: Recent GPU for iMac 2011 needed; flashing? (replacing failed 6970m)  (Read 53381 times)
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« Reply #90 on: January 30, 2017, 10:54:24 PM »

Do you think that the EFI & parts of the BIOS from the 8800M GTS would work? (attached) Currently running with the correct display mappings (I think) on the DCB but without any EFI at all, as this seemed to cause issues as it was the one designed for the 27 inch. I have been looking at the Nvidia spec, but not too sure exactly what I need to change with connector table entry where I think the hot plug signals are. I think it should start disabling and then enabling each one by one to find out which is which if i can do this in the same way as with the DCB section?

Any help appreciated !

EDIT: Gone back to the ROM Tried before the flash failed and booting in OS X as well again with EFI Boot on External Screen and unscrambled loading on external screen. Strangely OSX Then three quarter loads and neither screens come on but using remote access the iMac Display is detected as an iMac display however no external at all. I think as Florian suggests its the Hot Plug ID's?

EDIT: Just flashed with the below DCB Table and now OS X Works on the External Screen fully with EFI Loading Screen and when booted:

1F 0F 00 01 34 00 01 00
1F 1F 00 01 10 00 02 00
1F 2F 00 01 30 00 02 00
D6 5F 01 08 20 00 42 0F
92 5F 01 08 20 00 02 00
C6 4F 01 08 10 00 42 0F
82 4F 01 08 10 00 02 00
8F 3F 01 08 30 00 02 00
B6 8F 03 04 10 00 42 0F
72 8F 03 04 10 00 02 00
A6 7F 02 02 10 00 42 0F
62 7F 02 02 10 00 02 00
6F 6F 02 02 10 00 02 00
0F 9F 04 02 00 00 00 00

Going to try and mess with the LVDS soon and get internal as well (Hopefully)

EDIT: Rebooted and now not working again  Huh

* iMac21.rom (154.5 KB - downloaded 214 times.)
« Last Edit: January 31, 2017, 12:12:59 AM by richardhancock » Logged

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« Reply #91 on: May 27, 2017, 09:00:20 PM »

They already are being flashed.

All you need to know can be gleaned from images on EBay.

Some folks in China figured out which cards can be flashed. Instead of being mouthy idiots (like me) they just quietly started selling them. Since "flashed iMac video cards" isn't a thing, nobody asks or lists what they are .

I want to develop some roms, I bought 1 of each card but just haven't found the time. I also need someone in Hollywood with a 2011 iMac, preferably with an MXM cable that allows testing of cards outside machine.
sorry i did not see you reply, what is the device id i would need to look for? and where on the ebay cards would i find it or would it be listed, i want to get a cheap 6770m but all i see are ones from hp laptops and i am not sure if they would work or could be flashed to work with my 2011 27inch imac

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« Reply #92 on: March 26, 2018, 06:53:11 PM »


some time ago the Amd Radeon HD 6970m GPU of my iMac stopped working,
the computer is an iMac mid 2011, Sandybridge i7 originally with an Ati Radeon 6970M
We tried to fix it by doing reflow but it only worked 1 start more,
so we replaced it with an NVIDIA Quadro fx2800m, but it did not work either.

the computer when starting up, makes sound the CD unit and a little hard disk, but does nothing else.

I have extracted the BIOS directly from the chip on the motherboard, with a raspberry pi3 and a SOIC8 clamp.
and the ROM I have unpacked using the CHIPSEC application, chipsec_util uefi decode rom.bin

my intention was to edit the DSDT and SSDT files extracted directly from the rom, so that it starts from the Quadro FX2800m card or even from the integrated board that carries the Intel HD3000 imac,
and then go back to include them in the rom and reflashing
but at the time of editing these files, I see that they carry many references to other elements and I do not know exactly what should be edited,

Could this method work?

I attached the extracted DSDT SSDT files in case you can help me.

on the attached DSL files only in which it refers to IGPU or GFX0.
about the AML, I attach all.

Thanks in advance

* (19.14 KB - downloaded 67 times.)
* (18.85 KB - downloaded 60 times.)
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« Reply #93 on: March 29, 2018, 08:30:52 PM »

You guys should stick to known working cards or cards in same family as existing cards.

On AMD cards you need to match portmapping.

On Nvidia cards there are DCB tables. Only likely cards are Kepler using the EFI from iMac with 650.

Device id and DCB tables would need to be fixed.

None of this is easy, without ability to remotely test (MXM cable moving card outside ) and socketed EEPROM it will be extremely difficult.

Before asking a question, check your "Personal Settings" and be sure that you have "Brain Services" set to "On".

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« Reply #94 on: March 29, 2018, 09:32:10 PM »

Hello Rominator

and some way to disable this port - disable GPU card?
and that start only from the intel HD3000 Integrated?

I do not know if the method they use in the MacBookPro 2011 would work, since my computer is an iMac mid 2011

sudo nvram fa4ce28d-b62f-4c99-9cc3-6815686e30f9:gpu-power-prefs=%01%00%00%00

or from Linux

printf "\x07\x00\x00\x00\x01\x00\x00\x00"> /sys/firmware/efi/efivars/gpu-power-prefs-fa4ce28d-b62f-4c99-9cc3-6815686e30f9

the problem is that it does not start in any way, for which I can not execute any of these commands.

I have tried to edit the nvram variables of the rom, but without result, I do not know if I will be doing it correctly.

so what I've done, is to extract the rom from the computer and investigate it,
and from here I have extracted the DSDT SSDT files that I am trying to edit ...

I have seen this patch and I have adjusted it to the scheme that I have,
what I do not know if it would work,

// added to turn nvidia / radeon off
                        If (LAnd (LEqual (Arg0.3), LEqual (Arg1.1)))
                            External (\ _ SB.PCI0.P0P2.GFX0._OFF, MethodObj)
                            \ _SB.PCI0.P0P2.GFX0._OFF ()
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« Reply #95 on: May 25, 2018, 07:40:28 AM »

I don't know, at some point you should just yank the card out.

But you might also investigate that app that switches? If you read his notes is sounds like earlier version used power switching. So, it stands to reason that if you checked out how his older version worked you might discover how to do now.

And as to the guy working on 660M, how did that ever turn out?

Since Ebay isn't flooded with iMac 660Ms, I'm guessing it never got perfected.


Before asking a question, check your "Personal Settings" and be sure that you have "Brain Services" set to "On".
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« Reply #96 on: August 20, 2018, 04:11:19 PM »

I have a pure noobish question...

I have bought that GT660 for my iMac 2011 27".
It works great in macOS (no backlight, not boot menu as expected)

However it seems not to be working in Windows.
Is it because I haven't installed the drivers prior to swapping the GPU or it won't work out of the box?

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