Use a iMac as Monitor

[tllim]

Then i need to buy a new screen

Why? 'It might (not) work also implies the opposite'

I just don't know. The older 21" iMacs have a 1080p resolution (that's what Pine64 prefers) and customers use them as displays for nearly everything. But according to many reports here in the forums the Pine64 seems somewhat picky.

I still suspect that the HDMI issue we currently face with the BSP kernel currently used with every OS image is something similar as we had with the Ethernet driver: Allwinner delivered untested 32-bit code and when the 2GB Pine64 models connected an Ethernet cable the driver has been loaded and immediately crashed due to an integer overflow. And I would suspect it's something similar with HDMI: small bug (that is easy to fix) --> crashed driver --> no display.

But unfortunately the people running into this issue are not even thinking about starting to debug or at least look whether something crashed or not. So it's somewhat unlikely that any progress will be made the next time.

The HDMI driver in the BSP ver 1.2 is newer than the one in BSP ver 1.0. Allwinner mentioned the new one improve on the HDMIp60 handling. However, I will check with Allwinner whether the 32-bit integer overflow situation can happen again on HDMI driver in 2GB board. The new BSP ver 2.0 just released, which match with Android 6.0, I already have the SDK and will release out on next week.