iMac mid 2011 27" failing

[juicer52]

Started out with screen issues; flickering, lines, going to white. Computer not booting.
Genius bar couldn't even get it to boot. Said it's a goner. Don't waste time or money. It's obsolete. On an i7 with 16GB ram???
Fiddled with it to get it to boot and updated to High Sierra and all seemed fine but eventually failed worse.
Ran Linux Mint in compatibility mode perfectly from the live cd but realized that this bypasses the internal HD and probably bypassed a wonky AMD 6970M card .
In the process of trying to run LM from an external HD, I have somehow added a grub menu to the startup replacing Mac's normal startup. (created more problems)
Anyway, the external Linux HD created doesn't run or even show from Option at startup.
OK back to the original problem.
Cmd+R doesn't bring up the startup utilities screen. Runs internet recovery but eventually goes to white screen.
The computer could be used as a space heater. There is a lot of heat coming from the back. ?? bad graphics?
Installed High Sierra to usb installer but that starts then fails to white screen. Obviously not an external HD OS but I figured give it a shot.
This damned grub installer is highjacking anything I know how to do to get single user etc to run. Can that grub startup be bypassed or eliminated?
Is there a way from Single User command to disable AMD graphics and defer to Intel onboard? Thinking the AMD issue interrupts a testing cycle in booting?
Is all of this now a failing or dead HD.
The computer has an ssd boot drive and a 1TB storage drive (contents I'd like to preserve).
SOS

 

[chscag]

Welcome to our forums.

Normally, a NVRAM reset will get rid of the GRUB bootloader. But it sounds like your 2011 has numerous problems and likely not worth spending $$ to repair it.

The 2011 iMac models (both 27" and 21.5") were rather easy to get inside and do repairs. With some help from www.ifixit.com and the right tools you should be able to open it up and remove the SSD and the 1TB storage drive.

Your 2011 iMac does not have dual graphics. So if the AMD is defective, that's it. Nothing to fall back on as there are no built in Intel graphics on that model.

 

[juicer52]

Thanks for the heads up. There was a recall for the graphics issue but that ended many years ago now.
This computer belongs to a friend.
Not 100% sure about the graphics. If the graphics was an issue, how can the Linux Mint live cd run without any issues for days on end.
Tried the NVRAM reset but gnu grub screen still comes up first unless I choose Option key.. any other thoughts to rid myself of that bugger?
I am trying to create an external HD of High Sierra from an installer but the only Macs I have don't allow as the current OS is too new. Is there a way around this? If this box runs off an external HD, it might point to a dead internal SSD.
Apologies for the many and varied questions along this journey.

 

[jasongoldworthy]

the reason the linux live CD runs for days on end is because it don't load up the correct drivers for the GPU.

as for getting rid of the bootloader

if you can id format the Hard Drive as likely the boot loader is on there,

 

[juicer52]

By "correct drivers" would you mean the ones that are possibly causing a panic shutdown?
If that is the case, then perhaps there are other drivers that could be used with the Mac since the video image is stellar with Linux live CD.
There is no onboard Intel GPU as I had hoped but the sole AMD Radeon HD 6970 that was subject of recall many years ago.
Are using other drivers an option when it comes to Mac? This is unknown territory to me.
If it were software related, there might yet be hope.

 

[jasongoldworthy]

yes that's correct,

there is no other drivers that can be used under Mac sadly.

it will always try to get the ones built in to work.

best bet would be to source another GPU from eBay ??

the reason why the live cd is perfect its like running windows without the GPU Drivers installed.

so linux thinks its just a generic driver for the GPU

 

[juicer52]

It came to life briefly today but shutdown again. Have firewire in hand. Disks check out fine using FirstAID run in target mode from good imac.
Buying and swapping in a new gpu is money and time that I'm not sure is well spent here.
Once pics are off loaded, I may try a Linux install.

 

[jasongoldworthy]

I have the same machine and its still running strong for me.

I have it on high Sierra I know its getting old in the tooth now compared to newer OS's but it does what I need it for.

and id try a linux install if you can get along with it just make sure to back up all the pictures and so forth and then go whatever route you chose.