This is why higher-end Lumia phones can't currently run the Windows 10 Preview

[Windows Central]

Microsoft's Gabriel Aul has offered a technical explanation on why the just launched Windows 10 for phones preview cannot currently be used on higher-end Lumia smartphones, such as the Lumia 930, the Lumia Icon and the Lumia 1520.

Full story from the WindowsCentral blog...

 

[Alex Bayes]

Why can i not get the preview 10 on my 820

 

[xandros9]

Why can i not get the preview 10 on my 820

Allow me to quote the article, the one you should have read.

"The majority of Lumia phones, from our most advanced to the most affordable, can be upgraded to Windows 10. That said, for this technical preview, we need to start with a small subset of devices in order to isolate OS issues from hardware or board support package issues so we can stabilize the platform. This is a normal part of the engineering process, but you would not have seen it in the past because we haven't done a public preview before—so those builds were Microsoft only. (In the first 4-6 months of development, our team would typically focus on only one specific device—then we'd broaden.)"

Bold text is my touch.