[junkbit]

The spin-off Pure64 looks very interesting. It looks like they have factored out the code for getting up and running with your own project:

"The loader gets the computer into a full 64-bit state with no legacy compatibility layers and also enables all available CPU Cores in the computer."

"Two very simple kernels are included to get you started with your new 64-bit OS (One written in Assembly, the other in C)."

[zokier]

Pure64 also is proprietary :(

Is BareMetal bootable via GRUB?

[tessro]

I think that was just a poor choice of words.

They mean proprietary in the sense of "we built one ourselves". You can download source from the links at the bottom of the page: http://www.returninfinity.com/pure64.html

[zokier]

The distribution zip actually just contains binary pure64.sys file and sources for their example kernels. The sources for Pure64 are not included. Also, no information on licensing is included.

[wmf]

There seems to be some "64-bit" buzzwordism going on here. There's nothing special about 64-bit; it's just a different processor mode. Writing 64-bit code is no different than 32-bit.

[zokier]

AMD64 also included a lot more registers, and has some extensions to the instruction set. It also makes a baseline for other features like SSE, as all CPU:s supporting AMD64 are relatively modern. Also having larger address space to work with may affect some design decisions.

So while you can write 64-bit code just like 32-bit code, it's bit like saying that writing c++ is no different than writing c.

[Rusky]

64bit allows and/or requires different designs to be efficient. While the difference is usually negligible in user mode, 64bit in a kernel is rather different.