64 bit variables

[C3]

Now I am totally confused. There seems to be a lot of conflicting information around, or maybe I simply don't understand it.   

Didn't you already got the Intel 64 and IA-32 Architectures Software Developers Manual? Check MOV's manual page. Theres all possible ways to use MOV instruction, for both 32bit and 64bit use.

[zedd151]

@C3, nope. Reading that stuff makes my eyes bleed.   
I prefer explanations in plain language, from others with experience with such things.   

[C3]

@C3, nope. Reading that stuff makes my eyes bleed.   
I prefer explanations in plain language, from others with experience with such things.   

Well, I do not know Intel copyright policy of that manual, so I'm not doing a screenshot of one page.

[zedd151]

Thats okay, I have already googled for the reason and explanation. 
.. in addition to the info already posted here.

Pretty sure that mov mem,imm is restricted to a 32-bit value only.

[C3]

Thats okay, I have already googled for the reason and explanation.   

But another reason you to have the manual is.. that there is how instructions are build using machine language. So you can read and write the binary code/machine language. And I already know that you can do that too. But there is how the work is done by CPU Manufacturer.

[NoCforMe]

@C3, nope. Reading that stuff makes my eyes bleed. 
I prefer explanations in plain language, from others with experience with such things. 

Check out this page; it shows all the possible permuations of MOV.

Look at the end for all the variations that allow immediate values to be moved: notice that there are 4 sizes, imm8, imm16, imm32 and imm64. The only place that an immediate 64-bit value is allowed is when the destination is a register, not memory. (Keep in mind that r/mXX means "register or memory".)

It's not rocket science.