What is the iMac 2014 5K screen that runs Windows 8.1?

Windows 10 product key can not display 5K quality images like the Mac OS when running on the new 2014 version of the iMac.
Christina Warren, an editor at Mashable, skipped the 5K screen of the 2014 iMac by running Windows 8.1 product key.
According to Christina, she was surprised by this new technology from Apple. Thus, she tested Windows 8.1 product key on a 27-inch, 5K-resolution iMac to answer the question, "How does Windows process and display with a 5120 x 2880 pixel display?".

To do this, Christina used Boot Camp to run the Windows 8.1 operating system on the iMac 2014 hardware platform. As a result, Christina realized that, when booting into Windows, the driver recognized the resolution. 3840 x 2160 (Ultra HD) instead of 5K as the essence of the test iMac.
In addition, when entering the Desktop mode as well as launching applications on the interface of Modern UI (Windows Store, Xbox Music ...), office applications on the Desktop interface (Microsoft Office, Photoshop ...) All can not achieve the highest resolution.
One of the reasons is that AMD has not supported graphics card drivers used in the iMac 2014 to display 5K quality images on Windows product key.