nikey22

Sorry, I just logged in now Do you still have the GTX 880M installed in the imac? The GTX880M WILL work in a 27" imac 2011, because it is a Kepler based GPU. But you will lose brightness control, which makes things very hot and bright, and probably make the fans spin up a bit more. I would recommend staying with High Sierra for now. First lets gets some more information: What year is your computer? What size 27" or 21.5"? What do you mean by I paid someone to install it? What did they exactly do? You can't install the GTX880M without a heatsink mod (slight shaving off of the inner corners); How did they test it? Did they just give it back to you? You need a custom ROM for the GTX880M. Easily made. Did they flash some ROM in there? Probably not. You need some skills like learning how to use a CH341a_spi programmer (this will help a lot getting out of trouble with a bad ROM) You need to ID the flash ROM chip on the GPU board (easy) Get familiar with how to disassemble the imac. Its not hard, but there are steps that need to be followed and lots of little connectors, a good source is ifixit. You need flashrom for a linux based machine, like maybe ubuntu to do the flashing onto the ROM chip. Lets start with that.

a little late in replying, but here is one from TPU https://www.techpowerup.com/vgabios/161464/161464

No if you lost all the regions on the ROM (Flash Descriptor, ME region, BIOS, GbE), then you are correct you will need a full dump of the entire SPI image from someone else's machine (but you will have to change lots of things, serial number, MAC ID regions, UUID etc). But even if you got that, you will need to disassemble your computer and use a SOCI-8 clip and CH341a programmer to burn the new information back in. You will need to look for the EEPROM chip. There are probably 2, one for the EC and the other for the BIOS. Alternative is to buy a pre-programmed chip and either solder that yourself or have someone do that for you. The chip will probably be a Winbond and should start with 24 or 25. It will have 8 prongs. have a look at this http://forum.notebookreview.com/threads/official-alienware-13-r3-owners-lounge.797884/page-890, here someone had a similar problem with theirs after an bios update. Look at the picture to see what the EEPROM chip looks like. Practice dumping the info from these chips. A flash programmer like AsProgrammer_1.4.1 or even flashrom (linux) will be useful to actually read/write to the ROM chip. I'm still not clear, how much can you actually boot up to now? Does it POST? If you manage to dump the SPI image, upload it here so I can look at it.

From the iMac world, I can tell you, the majority of us use MX-4 Arctic for the CPU and K5-PRO viscous thermal paste for the thermal pad replacement that the MXM cards need.

have a look at this guide: https://na.alienwarearena.com/ucf/show/222700/boards/technical-support-1/ForumPost/urgent-aw-17-r2-bios-update-failed and here for some ROMs: http://downloads.dell.com/published/pages/alienware-13.html

For the 2011 iMac world, I'm looking to see if someone can mod the voltage, power and boost table to accommodate a 880M into these machines. The computer uses a 310W supply and the CPU uses 65W TDP (assuming a i7 2600s upgrade was done). The SSD barely uses any power, lets say 2W. Appreciate very much Johnksss (for the 780M) and svl7 (for the 770M, 765M) mods that were done. These are rock stable even with intense use prolonged use of the iMac. A good starting base for the mod would be the Dell ROM: Dell.GTX880M.8192.140309.rom attached A working model of an already modded ROM: 780M_EG2 attached Awesome work as usual! Dell.GTX880M.8192.140309.rom.7z 780M_EG2.7z

A lot of progress have been made since this post. the GTX 765M, 770M, and 780M GPUs and Quadro K1000M, K1100M, K2000M, K21000M can now display boot screens using a VBIOS mod. The EFI boot screen is still not reliably enabled (apple/progress bar/gray screen at beginning). However, once the Kepler drivers load up, the display returns just before the login screen.

This was a good idea, but the problem is that the 980M is a Maxwell GM204 architecture. For the 2011 iMacs, only Kepler based GPUs will work (GK1xx). This has to do with the fact that Apple has not created any Maxwell (-Pascal or -Turing) based efi or legacy drivers to include in the GPU firmware. There was never any reason to, because they decided that their future would be AMD based GPUs and re-partnered up with AMD.