Salvaging an old iMac

Fizzunk · Apr 13, 2014

I've been looking on eBay and there are cheap replacement Radeon 4670 256mb gpus going for around the $200 range.

Now considering I just want to use this old iMac as a monitor, supposing I use it as an external, the GPU from the new computer will be doing most of the work correct? Not the 4670 in the iMac?

Altemose · Apr 13, 2014

Fizzunk said:
I've been looking on eBay and there are cheap replacement Radeon 4670 256mb gpus going for around the $200 range.

Now considering I just want to use this old iMac as a monitor, supposing I use it as an external, the GPU from the new computer will be doing most of the work correct? Not the 4670 in the iMac?

I have no knowledge on Target Display Mode other than how to enable it. Perhaps Intell can chime in?

Intell · Apr 13, 2014

The GPU in the slave iMac would still be needed, but mostly in a passthrough sense. The basic framebuffer may be enough to be able to drive it. You could try removing the offending GPU kexts from the Extensions folder and starting up normally to see if it will work.

Fizzunk · Apr 13, 2014

Intell said:
The GPU in the slave iMac would still be needed, but mostly in a passthrough sense. The basic framebuffer may be enough to be able to drive it. You could try removing the offending GPU kexts from the Extensions folder and starting up normally to see if it will work.

Never used the terminal before

I quickly googled some commands, would this work?

> mkdir DisabledExtensions
> cd /System/Library/Extensions
> sudo mv ATIRadeonX2000.kext ~/DisabledExtensions
> sudo touch /System/Library/Extensions

Intell · Apr 13, 2014

Yes, that should work.

Fizzunk · Apr 13, 2014

Hey! Look at that it worked! I'm not in safe mode anymore!!!

So I can boot normally now, USB devices work. However my device still doesn't play any sound or movies. What exactly did removing the kext files do? Is it like removing drivers on a PC?

Intell · Apr 13, 2014

Removing that stopped the system from trying to use the advanced features of the GPU. Movies won't work and neither will anything that requires any video acceleration. Target Display Mode may work, but I'm not sure.

Fizzunk · Apr 13, 2014

So if the video acceleration is disabled, is the sound driver linked to that as well?

Either way I need a new gpu one way or the other huh...

I just left the house, but I'll try my ps3 when I get back.

Can't thank all the posters here enough for the help and support. Apple would've charged me $50 for what you all did on your own time! Much obliged.

Intell · Apr 13, 2014

I don't think the sound would be linked to removing the video kexts. Not sure why that isn't working.

Altemose · Apr 13, 2014

Fizzunk said:
So if the video acceleration is disabled, is the sound driver linked to that as well?

Either way I need a new gpu one way or the other huh...

I just left the house, but I'll try my ps3 when I get back.

Can't thank all the posters here enough for the help and support. Apple would've charged me $50 for what you all did on your own time! Much obliged.

No problem. I found the Apple Technician Guide for your iMac which in depth describes the procedure for repair. Check it out here! Hope it helps

Fizzunk · Apr 14, 2014

Intell said:
Removing that stopped the system from trying to use the advanced features of the GPU. Movies won't work and neither will anything that requires any video acceleration. Target Display Mode may work, but I'm not sure.

I can confirm for you that target display mode indeed does not work with the kexts removed

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Altemose said:
No problem. I found the Apple Technician Guide for your iMac which in depth describes the procedure for repair. Check it out here! Hope it helps

Oh wow! I never thought something like this would be around on the internet. I've seen a few guides on how to do it so I have a rough idea. None of them mentioned an ESD wrist strap. I guess it makes sense to be extra careful especially with taking apart a mac - given how crammed in it all is.

----------

Intell said:
I don't think the sound would be linked to removing the video kexts. Not sure why that isn't working.

Darndest thing, I've been testing it a bit more...

iTunes - no sound
Movies - obviously won't play
youtube - no sound
moving the volume dial up and down - no sound
uTorrent telling me a download has finished - SOUND

-_-a

EDIT: Figured it out, something about running it on safemode switched on my AirPlay and all my sound was defaulting to an external device for some reason. After disabling it, seems to be ok.

Altemose · Apr 14, 2014

Fizzunk said:
I can confirm for you that target display mode indeed does not work with the kexts removed

----------

Oh wow! I never thought something like this would be around on the internet. I've seen a few guides on how to do it so I have a rough idea. None of them mentioned an ESD wrist strap. I guess it makes sense to be extra careful especially with taking apart a mac - given how crammed in it all is.

----------

Darndest thing, I've been testing it a bit more...

iTunes - no sound
Movies - obviously won't play
youtube - no sound
moving the volume dial up and down - no sound
uTorrent telling me a download has finished - SOUND

-_-a

EDIT: Figured it out, something about running it on safemode switched on my AirPlay and all my sound was defaulting to an external device for some reason. After disabling it, seems to be ok.

ESD bracelets discharge the static electricity from your body to prevent damage to components. I am going to guess you are going to try and reflow the board by baking or using a heat gun?

Fizzunk · Apr 14, 2014

Oh nah, I'll probably buy a replacement card from eBay.

Altemose · Apr 14, 2014

Fizzunk said:
Oh nah, I'll probably buy a replacement card from eBay.

Ah. That Service Guide I linked to is a great resource as well as iFixit.

Fizzunk · Apr 18, 2014

For the curious, I set my PS3 back to 720p and I can confirm that TDM now works.

Even with 3D acceleration disabled by removing the KEXTs for the GPU.

Altemose · Apr 18, 2014

Fizzunk said:
For the curious, I set my PS3 back to 720p and I can confirm that TDM now works.

Even with 3D acceleration disabled by removing the KEXTs for the GPU.

That is good to hear. I am guessing you have no plans to repair the iMac?

Fizzunk · Apr 18, 2014

Well for the time being not really. It still does everything else I need it to do.

If I really wanted to watch videos I could copy movies to the PS3 and play it through that haha.

Have the prices for the 2009 Radeons always been around the $300-500 range? I get the feeling it's not going to drop anytime soon.

Altemose · Apr 18, 2014

Fizzunk said:
Well for the time being not really. It still does everything else I need it to do.

If I really wanted to watch videos I could copy movies to the PS3 and play it through that haha.

Have the prices for the 2009 Radeons always been around the $300-500 range? I get the feeling it's not going to drop anytime soon.

That money could easily start to afford a new iMac. Since you were planning on upgrading here is your opportunity. Even though the GPU is busted the iMac is still worth something. Give it a shot at selling it and make sure you fully disclose what's going on with it.

Fizzunk · Apr 30, 2014

Sorry to necro an old thread but I believe this is important.

I noticed that even with the KEXT files removed I can still view MP4 files in quick look.

This method even works if I convert any other format to MP4.

Unfortunately, perian has been discontinued so I don't know any other way to play files save for converting them using "any video converter".

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