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So I installed Windows 8.1 x64 using the Boot Camp Assistant on my Yosemite, iMac 5K 27".

The max screen resolution is being reported as 3840x2160.

I cannot explain what exactly is wrong, but my strain is huge after working in this setup for ~2 hours. It wasn't so in MacOS. I suppose the problem is with graphics driver.

I updated Windows 8.1 - everything I could.

What worries me is that the latest Boot Camp Support Software 5.1.5640 does not list iMac 27' 5K:

https://support.apple.com/kb/DL1721?locale=en_AU

.. and the AMD website where I wanted to try their driver here: http://support.amd.com/en-us/download/desktop?os=Windows%208.1%20-%2064

says:

This driver is not intended for use on AMD products running in Apple Bootcamp platforms. Users of these platforms should contact their manufacturer for driver support.

Then, I tried to contact Apple Support - I have an extended support for 3 years (AppleCare). They asked me nicely to go and ask Microsoft for this.

Finally, I contacted Microsoft Support and they proposed that I subscribe to their support service (e.g. spend another $100+) and they will solve my issue. They assured me they knew the solution and they even had an internal technical note about a similar case. Besides the feeling of being cheated, I supposed there should be drivers for my case, but I can't find anything.

Please help me - how else can I try to solve the issue, what system info you want to know in order to give advice, and where should I look for more references / reading?

UPD. I've also tried these drivers from AMD designed for BootCamp, but it did not help: http://support.amd.com/en-us/download/desktop/bootcamp

  • Did you download the latest Support Software as suggested here? "BCA: Use Boot Camp Assistant (BCA) to download the latest Boot Camp software. The support software available from Boot Camp Assistant is newer than what is currently available as a manual download." – klanomath Apr 18 '15 at 10:43
  • Yes - I let the Assistant download drivers for me and put them on the USB flash drive. – Meglio Apr 18 '15 at 10:55
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    AFAIK the Boot Camp drivers haven't been updated in over a year (even when they are "updated" it's usually just a change to the package to allow installation on a newer model and no actual driver changes). The 5K iMac is much newer than that and it stands to reason that Apple have not sourced any drivers for it yet. – Stuart H Apr 18 '15 at 12:47
  • Apple Support said Boot Camp Assistant can download newer drivers then the ones available for download from the Apple Support website. However, letting Boot Camp Assistant to download drivers for me and put them on my USB flash drive, and then installing them on Windows - did not help. – Meglio Apr 20 '15 at 12:43
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    Known issue. I haven't delved deeper into the topic, but it's mentioned here, here, and here with a (supposed) solution. Good luck, but it seems that you'll have a lot of issue with this, if nothing else because of the three different companies involved (Microsoft, AMD, and Apple.) – JMY1000 Mar 7 '16 at 5:22
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Back in 2015 there was a Bootcamp Update that came through Apple Software update (ATI/AMD driver), which enabled full 5k resolution for Windows 8.1.

Sadly Apple pulled this update silently. I only know the version number of that gorgeous driver: 15.201.2001-15005a-295390C

But the only way to get it, is a private person, which did that update and did not delete the installer, usually located in: "C:AMD/".

If I once get that driver back, I will share with everyone! Maybe someone can help?

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Update 1:

Did you check Apple Software Update. The updater should be installed on you computer.

Also, try Windows update. Most of the time any additional drivers will be listed as optional updates. You should also make sure the box: "Give me recommended updates the same way I receive important update" is checked off.

(Ok, I see where you said you did all the updates already)


The instructions from Apple say to download the drivers using Boot Camp Assistant.

See System requirements to install Windows on your Mac via Boot Camp.

After launching the Boot Camp Assistant, there should be a check box something like below:

enter image description here

Did you install Windows with using the Boot Camp Assistant? Also, I assume you know how to change the resolution of your display once windows is installed.

On some models, the brightness is adjusted by clicking the Boot Camp icon on the Control Panel.

  • I did follow all official guides found on Boot Camp Help Pages and ended up with maximum resolution being ~3.5k on my windows. Only then did I try downloading different Boot Camp Support Software versions, as well as drivers directly from AMD website (they have Boot Camp Drivers section as well). Nothing helps. – Meglio Apr 18 '15 at 10:48
  • @David Anderson can you (or anyone else) confirm that this is possible and that it works, or is your answer here more of general guidance? – ardave Aug 1 '15 at 0:25
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The answer could be that Windows 8.1 simply not ready to manage that kind of resolution. Yet.

  • Pretty sure this isn't the case, 5K monitors like the Dell one work with Windows. – JMY1000 Jun 14 '16 at 0:45
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From a little research I was not able to find anything that actually described getting the full 5K out of the iMac if you're on Windows.

From a dated Mashable article:

From what I can gather, that's because AMD hasn't updated its driver for the graphics card inside the iMac to support 5K. So at the time of this writing, the maximum resolution the display can use is 3840 x 2160.

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