Intel 64 , how to switch modes

[saurabh]

Hi all,

I am new here and this might have been discussed earlier but I did not get my answers so asking here. Please point me to links or provide explanations.

The QUESTION :

On 386 or IA-32 (well I know that is a thing of past), you boot in real mode, turn on a bit in CR3 and you are in protection and then you turn one more bit on to switch on paging.

Ok the REAL QUESTION:

What is the boot sequence on Intel 64 or (if you allow AMD 64 processor), in terms of processor modes.
How does the software decide it has to be in legacy mode, compatibility mode or 64 bit mode.

Which registers /bits need to be manipulated to achieve that.

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P.S.

I know I have been really naive, but I have googled a lot, I end up with links to AMD and Intel marketing pages boasting but with not technical details.

I barged into Intel 64 system prommar's manual and have not found anything useful. I haven't gobbled it but maybe I am just naive.

[saurabh]

It would have been good if I had looked in the chapter 8 of the manual. I have got my answer thank you.

[martini161]

Glad you got it sorted out