Up to gtx 780 mxm 3B Kepler cards will work in 09/10/11 21.5 and 27 iMacs… I would use 765m 2gb mem must have dell , Alienware bios or you can flash it your self… Not as difficult as it sounds… Cards are available on ebay for 99 and up . These work without any hacks on Mojave and allow graphic acceleration without any further tweaking. I’ve only tried the 2011 but others have done it 2009 and 2010 iMacs and I can’t see any reason why it wouldn’t… there is apple driver support natively built into Mojave for Kepler architecture this will probably end with Navi. You will still also need the Mohave upgrader kit from dos dude unless you have a hard drive with Mohave already installed. somebody probably has a video out by now … I would check for that. Update (02/19/2019): chip flashers that were supposed to be included wit the above comment Update (02/19/2019): If you need to flash a chip before you install it or because you bricked your bios, there is 2 very good and inexpensive options I use... the small black...
Watch this video it’s the third of three but you can probably locate the other two if you wanted…It will give you a look at what’s in the box and some colourful commentary….https://youtu.be/EdwDvz47lNw
Yes you can use any Apple mxm 3 a/b graphics card it’s just plug and play…the letters a/b are the sizes, a/ being the smaller size for 21.5. The b cards although bigger can still fit by removing a piece of plastic, you’ll see what I mean once your in there… It’s really easy get yourself a step by step guide if you haven’t taken one apart before.
I had a similar problem not sure if it’s exactly the same as yours without seeing your machine… The first time it happened I did an internet download of a new operating system… Then it died again a little while later maybe two weeks or less I hardly use it so I’m not sure but it wasn’t very long…At this point I’m pretty sure it’s a faulty hard drive. The other thing I noticed was the hard drive no longer showed up in disc utility… I like to play around with old iMacs as a hobby so I have an external SSD with an apple os on it… I plugged it in via external usb 2.0 on the back and it boots every time... I’ve picked up a couple of Samsung SSDs and I’ll replace the 1tb disc drive with those. I’ll see if I can add a picture to this.
If you want a good quality thermal paste use arctic silver, you should be able to pick it up for under 10… I wouldn’t worry about getting the most expensive version the basic one is more than you should need. The reason it works so well is the silver content, it helps transfer the heat at a higher rate. If your a little nervous and you want to go all out, thermal grizzly it’s a liquid metal… Anything that I take apart with a CPU that’s a couple of years old I’ll usually refresh the thermal paste anyways, and with the old iMacs I hit the gpu as well.... I didn’t notice you already have the upgraded version of arctic silver… Good luck with your repair.
There’s no way to connect it to a Gen 3 x4 PCIe lanes within the PCH. I don’t even think your CPU/PCH has support for that, back then it would have been AHCI/PCIe Gen 2 which is much slower then what your M.2 needs, even if you could connect it… The most speed you can get will be from Samsung Pro SSDs, optimized with Samsung magician in RAID 0, still very fast. I would also do a RAM upgrade to 16 GB if you haven’t done that already. Even if you decide to use only one SSD and upgrade the RAM this will give you the best performance gain for the money.
I bumped up the ram in mine to 32 GB and put two Samsung SSD’s in RAID 0. It runs better than new! I also upgraded the OS to High Sierra. 2011 was the year they upgraded the SATA bus speed from 3.0 Gb/s to 6.0 Gb/s. Make sure you run Samsung magician on your SSDs before you install them in a RAID 0 configuration. I was never a fan of hybrid drives but I've heard people have good results with those as well. Anyways good luck with your upgrade which ever way you decide to go. Nothing better than the feeling you get when you fire up youir little guy for the first time and he's faster and better than before... Four out of five voices agree. Just out of curiosity I checked too see if the i7 2600s was still around and too my surprise you can still buy a brand new one from Newegg... Amazing... The s processor is a 65 watt TDP and the only upgrade that works in a 21.5 2011 iMac. I installed a used one, not thinking you could still buy them brand new. Oh yes, I almost forgot... Your 2011 has a 10 Gb/s ThunderBolt...
Try an external hard drive with an apple operating system installed… If it’s not your hard drive plug it into an external monitor and if you get a picture it’s not your hard drive. I don’t know how many chimes you got but that could also be the ram.
I would also try taking the hard drive out of the case and plugging it directly into a motherboard… If that doesn’t work there are companies that can retrieve data from damaged hard drives… When you get your little guy fixed I suggest backing up regularly to a cloud service… I think everything will work out fine for you it’s not as bad as it looks.