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Can I bypass the video card on a iMac?

M

Milaf

macrumors newbie
Original poster
Jul 10, 2012
8
0
Hello everybody,

I am new here as a registered user, but I have been around as a quest for a while!
Like many of you I am patiently waiting for the new iMac to come out.
My early 2008 24" iMac as a bad video card, so I tried connecting it to a different monitor, but the video card just displays the same garbage on the other monitor, Is there a way to bypass the iMac video card so that I can use the other monitor (and my computer), until the new iMacs come out?

Thanks for any help.
Michel
 
M

Milaf

macrumors newbie
Original poster
Jul 10, 2012
8
0
Yes the video card is bad!

Connecting my iMac to a seperate monitor was one of the ways I confirmed the problem was with a defective video card.

Michel
 
M

Milaf

macrumors newbie
Original poster
Jul 10, 2012
8
0
OK! Thank you Flatfoot, that's what I wanted to know.

I quess I'll have to suffer along with all the other people waiting for the new iMac's to come out.

Let's hope it is in July...

Michel
 
AppleDApp

AppleDApp

macrumors 68020
Jun 21, 2011
2,413
45
you need a video card to display an image. Unless you can rig an external GPU to your iMac (not possible) You will get the same image. Your GPU is faulty.
 
theSeb

theSeb

macrumors 604
Aug 10, 2010
7,466
1,893
none
You cannot bypass the GPU for the internal monitor unfortunately.

How does that USB out work? Surely it's still using your graphics card?

Edit: Never mind. I see the USB devices are actually separate graphics cards, but connected via USB to the computer instead of PCIe. I've never bothered to look into this since it's so slow, but I guess it's better than not seeing a picture at all.
 
marzer

marzer

macrumors 65816
Nov 14, 2009
1,398
123
Colorado
omvs said:
if screen sharing is on you could do it from another mac.
Click to expand...

A graphics card doesn't only drive the connected monitor, but performs all the graphical rendering regardless of the output device. The OS graphical interface relies heavily on the graphic card and the graphic card memory buffers. Without a properly working graphics card the OS is likely not functioning properly either. So I would doubt you will get screening sharing to work either if it is a malfunctioning video card.
 
B

bogatyr

macrumors 65816
Mar 13, 2012
1,127
1
You could search for a used video card board for your model iMac and replace your broken one.
 
O

omvs

macrumors 6502
May 15, 2011
495
20
Nyy8 said:
Sorry if I am being a bit of a noob, but doesn't every CPU come with a built in GPU on the CPU chip?
Click to expand...

Pretty sure no CPU's had an integrated GPU in 2008 (which is what the poster has).

And even if the CPU does have one, the main board might not expose it. For example, it looks like the CPU in my iMac has a HD 3000 onboard, but only the ATI 6970 is hooked up to the ports...
 
M

Milaf

macrumors newbie
Original poster
Jul 10, 2012
8
0
Thank's everybody for your imput.

I tend to agree with marzer's response!
I tried connecting the iMac to two different types of monitors, and nothing comes out differently than what I see on the iMac. And yes, other functions are affected also. The cursor does not appear on screen, so I move the mouse around until I see the icons in the dock grow bigger when I pass over them, and then I try to align myself with whatever I am trying to click on. It's a little bit like playing batteship in the dark!!!

Anyway thanks for your help.

Michel
 
R

Rlnplehshalo

macrumors regular
Jan 28, 2011
146
0
By garbage do you mean the image somtimes burns into the screen but not really the actual screen more so the GPU? I have the same iMac and same problem:( For example when browsing the web on a white webpage I can see my desktop icons through it, I've tested this many times and it never goes away. I'll be building a custom PC in a few weeks anyway no more problems for me!
 
P

Puevlo

macrumors 6502a
Oct 21, 2011
633
1
Rlnplehshalo said:
By garbage do you mean the image somtimes burns into the screen but not really the actual screen more so the GPU? I have the same iMac and same problem:( For example when browsing the web on a white webpage I can see my desktop icons through it, I've tested this many times and it never goes away. I'll be building a custom PC in a few weeks anyway no more problems for me!
Click to expand...

By garbage he means it still displays Mac OS X. The only way to get rid of this is to install Windows onto the computer.
 
M

Milaf

macrumors newbie
Original poster
Jul 10, 2012
8
0
Rlnplehshalo said:
By garbage do you mean the image somtimes burns into the screen but not really the actual screen more so the GPU? I have the same iMac and same problem:( For example when browsing the web on a white webpage I can see my desktop icons through it, I've tested this many times and it never goes away. I'll be building a custom PC in a few weeks anyway no more problems for me!
Click to expand...

Not exactly!
By garbage I mean the desktop background image looks like a psychedelic version on crack, and there are also some patterns that appear that are not in the image. I dont know if I can post pictures, but if I can, then I could put up a picture.

Michel
 
Hirakata

Hirakata

macrumors 6502
Mar 17, 2011
314
400
Burbank, CA
marzer said:
A graphics card doesn't only drive the connected monitor, but performs all the graphical rendering regardless of the output device. The OS graphical interface relies heavily on the graphic card and the graphic card memory buffers. Without a properly working graphics card the OS is likely not functioning properly either. So I would doubt you will get screening sharing to work either if it is a malfunctioning video card.
Click to expand...

This is not entirely accurate in my recent experience. The 8600M died on my MBP. The MBP's display showed nothing and neither did connecting an external monitor. Apple Store confirmed the graphics card was dead. I was still able to screen share to the MBP and backup the HDD without a problem.
 
M

Milaf

macrumors newbie
Original poster
Jul 10, 2012
8
0
awer25 said:
Is the GPU removable like the newer iMacs? Maybe you could get a new one?
Click to expand...

I believe it is possible.
I have looked at a few videos of someone actually changing one, and you have to remove just about every component of the inside of the iMac to get to it. I've been told the price to have this done by a repair shop would be exorbitant!
But if I can find a used card for cheap, I would like to attempt to do the job just for the fun of it, and maybe end up with a spare iMac.

Michel
 
S

strnbrg59

macrumors newbie
Jan 21, 2015
5
0
California
Problem solved

Milaf said:
Safe mode is the only way I can actually get to use the iMac, but only under all of the conditions I have mentioned before!

Great, that was exactly the right question to ask. In safe mode, your iMac skips over loading the device driver for your video card. Contrary to some posts here, your iMac *can* function without that driver, quite well in fact; the buffering in that case is done in software, rather than hardware, so it's slower but plenty good enough unless you're a gamer.

So you could just boot into safe mode every time, but that carries the disadvantage that about two dozen other device drivers (like the ones that handle Wifi and sound) are also not loaded. What you want to do, then, is arrange for your system to boot with all its device drivers *except* for the video one. For step-by-step details, go here:
https://forums.macrumors.com/showthread.php?p=20621409#post20621409
Click to expand...
 
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