Upgrading non-retina iMac with a Retina display?

[Strategia]

My 21.5" 2013 iMac has a decidedly non-Retina (1080p) display. It works great on unsupported Big Sur, but clearly Apple is no longer optimizing visual elements (like Control Center) for non-Retina displays. By using a 21.5" 2015 or even 2017 panel, I am thinking it may be possible to upgrade the screen to 4K @ 60Hz. I already have experience with opening up the machine as I recently upgraded the "non-user-accessible" memory and storage.

I am unsure of whether the integrated GPU (Intel Iris Pro Graphics 5200) can even drive a Retina panel. Intel lists the GPU as capable of driving a 3840x2160 display at 60 hertz. Promising, but Wikipedia lists the 21.5" 4K iMac resolution at the slightly larger 4096x2304. Someone with a Nvidia GPU would likely have no issue in this department.

Comparing the display connectors using iFixit display replacement guides appear to show that the cables are the same. Someone with a keener eye might spot the difference I am overlooking.

2013 21.5" iMac:
https://guide-images.cdn.ifixit.com/igi/RuoSZ5iXxQqvKfcF.huge
https://guide-images.cdn.ifixit.com/igi/2CYaRvZMKD1MHJWF.huge

2015 21.5" iMac (Retina):
https://guide-images.cdn.ifixit.com/igi/LhWm4T3JEHaeoZ2T.huge
https://guide-images.cdn.ifixit.com/igi/bRPraRvEkFJQYPsa.huge

Has anyone ever tried this, or am I just crazy? I guess there is only one way to find out if this works.

 

[TwoH]

Hi.

Im very certain this isn’t doable. LVDS connector on the retina has a lot more pins than non-retina.

And those ifixit pictures of the 2015 aren’t from an actual 2015, as you can visibly see ram - even though ram is soldered to the board for these models.

 

[Fishrrman]

Probably a waste of time and money.
Put that money towards a new Mac.

 

[Amethyst1]

I am unsure of whether the integrated GPU (Intel Iris Pro Graphics 5200) can even drive a Retina panel. Intel lists the GPU as capable of driving a 3840x2160 display at 60 hertz. Promising, but Wikipedia lists the 21.5" 4K iMac resolution at the slightly larger 4096x2304.

The Iris Pro 5200 has a 540 MHz pixel clock limit (source; page 148), which is enough for 4096×2304 at 53 Hz using CVT-RB timings (calculator). I haven’t tested if that GPU will actually output a 4096×2304 resolution to begin with though. I have the hardware to test this - shall I, in the name of science? But even if this doesn’t work, the Late 2015 Retina 4K iMac's panel also has a 3840×2160 60 Hz mode listed in its EDID, so…

A Nvidia Kepler GPU will do 4096×2304 just fine (proof) - at 53 Hz, due to the same 540 MHz pixel clock limit (source). The same applies to an AMD Radeon HD 7000 series or newer GPU (proof).

All this doesn't tell us anything about whether the Late 2013 iMac can actually drive an internal 4K panel though, so it remains purely academic.

 

[Nguyen Duc Hieu]

I am unsure of whether the integrated GPU (Intel Iris Pro Graphics 5200) can even drive a Retina panel. Intel lists the GPU as capable of driving a 3840x2160 display at 60 hertz. Promising, but Wikipedia lists the 21.5" 4K iMac resolution at the slightly larger 4096x2304. Someone with a Nvidia GPU would likely have no issue in this department.

Comparing the display connectors using iFixit display replacement guides appear to show that the cables are the same. Someone with a keener eye might spot the difference I am overlooking.

You can test the iGPU capability easily.
1 mDP to HDMI 2.0 cable.
Connect the iMac to your 4k TV set.
Moving the mouse to see if it's smooth.

 

[Amethyst1]

You can test the iGPU capability easily.
1 mDP to HDMI 2.0 cable.
Connect the iMac to your 4k TV set.
Moving the mouse to see if it's smooth.

That’s easy. The Late 2013 iMac has Thunderbolt 1 (DisplayPort 1.1) and will not run 4K at 60 Hz on an external monitor. 4K at 30 Hz will work.

 

[Amethyst1]

You know what - the Late 2015 21.5" iMac was available with either a 1920×1080 or a 4096×2304 display, with both systems having the same GPU. I wonder if a display swap is feasible with that generation.

 

[Strategia]

I have the hardware to test this - shall I, in the name of science?

Go ahead! Share your findings with us. While I agree this isn't very economical, it will be an interesting experiment. If TwoH is right, perhaps the retina connector can be soldered on?

 

[Amethyst1]

Go ahead! Share your findings with us.

Hardware:

MacBook Pro Retina, 15", Late 2013 with Intel Iris Pro Graphics 5200 -> Wacom Link Plus -> 21.5" LG UltraFine 4K (4096×2304 native)

This monitor uses the same panel as the 21.5" Retina iMac.

Result:

3968×2232 at 57 Hz

is the highest 16:9 resolution the GPU will output - on macOS High Sierra v10.13.6 at least. That mode actually looks fine on the panel, and so does the pixel-perfect 1984×1116 HiDPI mode.

 

[Strategia]

That mode actually looks fine on the panel, and so does the pixel-perfect 1984×1116 HiDPI mode.

Very promising! Now all that remains is for some brave soul to try grafting the same panel on internally. Honestly, not sure if I have the time to do so, but at least we know it wouldn't be completely impossible.

 

[Amethyst1]

Very promising!

You know what's weird? My 2011 MacBook Pro with Intel HD Graphics 3000 can run full 4096×2304 (at 27 Hz but that's beside the point). Yet a newer and substantially more powerful GPU cannot…

 

[TwoH]

2015 retina connector

2013 connector

LVDS difference

believe it’s 30 pin compared to 40 pin

 

[iLazarus]

since this is the only thread I could find that is somehow relevant on this topic, has there been there any progress on this?

can one replace/upgrade an old iMac 2009-2011 to a 4K/5K Retina display?

with an upgrade of the GPU that could easily handle higher resolutions, the main problems are the connectors of the LCDs? or what else needs to be done?

isn't there a "panel" similar to what is used when transforming an old 2017 iMac to a 5K monitor??