I've been trying to make this work, but I haven't been able to. Is there any way I can use the 2008 iMac 27in as an external monitor for my 2019 iMac 27in?
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Using a 2008 iMac 27 as an external monitor for a 2019 iMac 27?
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I'm not an expert, but I've read responses to the same question before because I also have a 2019 27" iMac and I was interested. My recollection is that it was always IMPOSSIBLE for 2019 machines, unfortunately.
Thanks for the reply. I wonder why they made it like that.
I think I read that only models 2009 and newer can be used as an external display.
1. Open the 2008 iMac.
2. Check the model number of the LCD board.
3. Buy a compatible LCD driver board
4. Now gut out everything else inside the iMac 2008 and install the LCD driverboard + Power adaptor.
5. Enjoy the result.
Thanks. I’m not very skilled at this. Is is a complicated process to exchange the LCD driver board and power adapter?
It' depends on how you define "complicated".
If you don't know how to use a screw driver, cut and join electric cable, then yes, it's terribly complicated.
Otherwise, not very complicated.
Is there a 27-inch model from 2008? I thought the first one is from 2009. Anyway, have you tried Apple's own directions for this?
There is no 2008 27” iMac.
2009 and 2010 27” iMacs (and only these) can be used as a display with any DisplayPort source.
Since a 2019 iMac has USB-C, you need a USB-C to Mini DisplayPort cable.
The 2009/2010 iMac should also be running macOS High Sierra or an older version, since the switching to an external source is done by a component in these macOS versions.
If these requirements are met, the older iMac will switch to Target Display Mode as soon as it detects a signal coming in via Mini DisplayPort. However, it must be fully booted up into macOS for this to work.
2009 and 2010 27” iMacs (and only these) can be used as a display with any DisplayPort source.
Since a 2019 iMac has USB-C, you need a USB-C to Mini DisplayPort cable.
The 2009/2010 iMac should also be running macOS High Sierra or an older version, since the switching to an external source is done by a component in these macOS versions.
If these requirements are met, the older iMac will switch to Target Display Mode as soon as it detects a signal coming in via Mini DisplayPort. However, it must be fully booted up into macOS for this to work.
This is a pretty popular topic, it seems. The feature you're looking for is called "Target Display Mode" and unfortunately, Apple discontinued it after a very short life. Hardware mods and software solutions have both been discussed in various threads, both in this forum and elsewhere.
For hardware mods, we have YouTuber Luke Miani converting a 2014 iMac into an external monitor. His work can of course be applied to other generations of iMacs, with the appropriate research. For software solutions, I had an interesting conversation with a guy who thinks he may be onto something, over on page two of this thread.
For hardware mods, we have YouTuber Luke Miani converting a 2014 iMac into an external monitor. His work can of course be applied to other generations of iMacs, with the appropriate research. For software solutions, I had an interesting conversation with a guy who thinks he may be onto something, over on page two of this thread.
I'm pretty sure that it's possible though I don't have the hardware to test it myself. The 2008 iMacs were 20 and 24 inches I think.
Software-based solutions can be laggy though.
Target Display Mode makes the iMac behave like a “real” display: no lag. There’s a direct DisplayPort connection between the host and the iMac’s LCD.
They can be so it depends on what you are doing and your monitor resolution. In this case, it's likely a 2008 24 inch which is 1920x1200. That should be fine over GB Ethernet. This solution seems to work fine, even at QHD:
If you need 5k, then you will probably have to set up a local Thunderbolt network between the two systems. At 10, 20, or 40 GBPS, it should be more than enough.
I have a 5k iMac and have tested this with scaled resolutions and it works fine but I'm curious if it will work at native resolution. I suspect not but would like to try the local wired Thunderbolt solution one of these days. I am using my iMac for actual work at this time though.
We don’t definitely know whether the OP have a 2008 or 2009 iMac yet. If it’s 27” it must be a 2009 (or newer).
Since scaled HiDPI resolutions use a framebuffer four times as large, running at native 5K should actually be less demanding. Unless you tested the “low-resolution” modes.
I tested with the iMac at scaled resolution (the highest one) and then created a share into the mini that was less than the size of the scaled resolution. So it was a screen sharing window, just like any other program. And it worked fine. The 2014 iMac has an i7, 32 GB RAM and the high-end video card so performance isn't a factor.
The gating factor for 5k native resolution would be the bandwidth over Ethernet. I do not think that GB Ethernet would be enough.
The Core 2 Duo 2009 iMac 27 has a pretty weak CPU and Target Display Mode gets it running pretty hot. The 2010 iMac 27 is quite a bit better in that regard.
That does not answer whether it was a HiDPI or non-HiDPI scaled mode.
Putting an iMac into Target Display Mode does not put any additional load on its CPU.
I'm unaware of any such setting on a 5k iMac. I simply set the resolution to scaled mode in Display Settings.
Have you verified that TDM does not use the CPU at all? This is one of the things that I had planned to test.
That’s a HiDPI mode. These use a framebuffer four times the size of the mode (e.g. 6400×3600 for a scaled 3200×1800 mode) and are thus more bandwidth-intense than native, unscaled 5120×2880. You can verify this by taking a screenshot and looking at its dimensions — they’re twice as wide and twice as tall as the scaled mode unless you go for native 5120×2880.
Yup. TDM switches the iMac’s LCD’s input from the iMac itself to the external source. It’s like having a monitor with two inputs.
I tested scaled QHD on the 5k iMac yesterday and it was fine playing full-screen video over Ethernet. The program that I use, though, doesn't support the other scaled resolutions (I need to add them to test them). It also supports the native resolution and I need to test that as well though I don't know how useful it will be.
Something about running TDM does generate a lot of heat. I'm going to see if I can look around on the system while it is running TDM to see if it's using system resources.
You can — enable Screen Sharing on the iMac and connect to it using that. The iMac keeps running normally while TDM is active.
It would be cool if you checked and compared the network traffic caused in both cases (via Activity Monitor).