iMac 27 L2009 hangs during start up, but can I still connect Mac mini?

[Dannydematio]

I have a late 2009 iMac 27 that developed a problem where it constantly hangs during startup. Weird lines around the cursor too, and won't start up from any external drive, it always hangs/crashes. I tried absolutely everything, all HW resets etc, so it's the logic board or graphics card. I've written it off but the screen is still excellent. I am wondering can I connect a mac mini and use it as a screen without having to fully boot up and pressing the key combination?

I can actually still get into this iMac in safe mode, but don't know how long that will last, or if it would even work from safe mode. It would be a safer bet if I knew I could definitely use it as a 27' monitor without having to boot up, just turn it on and connect.

Chicken and egg coz I don't have a Mac mini to test it out, but I could get one if I thought it would defo work!

Which cables do I need anyway, and which Mac mini would you suggest to be a good buy to last say 18 months as a stop gap before I move up a silicon iMac. I don't need the latest (expensive) iMac, only need the same performance or better than my old 2009 iMac 27 2.8 quad core i7 2TB ATI Radeon HD 4850 512!

I have a strong feeling your gonna tell me you need to boot fully into the iMac to get the display port connection working 😔 So safe mode is the only hope.

Lots will say just get a used iMac if you wanna wait, but sad to see a good screen go in the bin and I could give the old girl a few more lashes of life, if Technically possible.

 

[Boyd01]

This thread has some information about Target Display Mode, which is what you would need to enter on the iMac. Sorry, I am not familiar with the 2009 iMac. You might need to use firewire on a computer that old. If so, then the 2012 Mini is the last model that has a firewire port.

2018 Mac Mini with 2011 iMac as Second Display

The Mid 2011 21" iMac has a feature called Target Display Mode. It is no longer supported as of High Sierra, but people are reporting that it still work with the source Mac with Mojave and Catalina. It will require an expensive adapter that only Apple Makes, the bidirectional TB2/TB3 adapter...

forums.macrumors.com

 

[Fishrrman]

If you can get into the iMac using Safe Mode, then it's time to get an external drive and clone the contents of the internal drive to a backup (before it quits altogether).

Use either CarbonCopyCloner or SuperDuper.
Both are free to download and use for 30 days, creating the backup will cost you nothing.

If it boots in safe mode but not into "regular boot", that suggests a failed [discrete] GPU. I believe safe mode by-passes the GPU and instead uses the CPU's internal graphics from which to boot.

I don't know whether target display mode requires the discrete GPU or internal graphics, perhaps others can answer.

If you don't have a Mini, then there's no point in going further.
I WOULD NOT spend money in a pursuit of something that may not work anyway.

But again, if the old iMac will boot/run in safe mode, use it that way.
And get the internal drive cloned right away.

 

[Dannydematio]

If you can get into the iMac using Safe Mode, then it's time to get an external drive and clone the contents of the internal drive to a backup (before it quits altogether).

Use either CarbonCopyCloner or SuperDuper.
Both are free to download and use for 30 days, creating the backup will cost you nothing.

If it boots in safe mode but not into "regular boot", that suggests a failed [discrete] GPU. I believe safe mode by-passes the GPU and instead uses the CPU's internal graphics from which to boot.

I don't know whether target display mode requires the discrete GPU or internal graphics, perhaps others can answer.

If you don't have a Mini, then there's no point in going further.
I WOULD NOT spend money in a pursuit of something that may not work anyway.

But again, if the old iMac will boot/run in safe mode, use it that way.
And get the internal drive cloned right away.

Thanks for the suggestions.

It's definitely the GPU and I cannot boot from any external drive even from safe mode. It hangs indefinitely or crashes and hangs.

I've written it off. I already had an up to date CCC clone so I have everything.

I've ordered a 2020 iMac 27' however, I have a two week lead time till delivery and I'm thinking the new machine may ship with Big Sur, which is a problem for me because I have a mission critical app that won't run only runs on Catalina.

Can I take the new 2020 iMac back to Catalina or would I be better off to install Catalina onto an external drive and just boot into Catalina when I need to use that app or they update.

Many thanks.

 

[DeltaMac]

Big Sur is not released yet, still in beta testing. Highly unlikely it will be released within the next two weeks (and equally unlikely that your new iMac would arrive with Big Sur installed before final release of that system) Even so, you could expect that you can erase the drive, and install Catalina - current iMacs will certainly be OK with Catalina.

What app would you be running that runs in Catalina, but NOT in Big Sur?
Catalina is already 64-bit apps only, so it can't be a 32-bit app that you might be using. (You may find out that your critical app may run in the final release of Big Sur.)