Can anyone tell me what the memory mode is at the time linux kernel is loaded (by bootloader)? As this link says, the memory mode is real mode then the linux kernel will ask user to choose video mode and then switch to protected mode, but I do not seen it ask me to choose any thing, so is it right?


From what I understand of the x86 architecture and the Linux boot process, when the computer is turned on, it is in real mode; the kernel then enters protected mode after setting the needed descriptor tables. This is done by the code in the files pm.c and pmjump.S.

The diagram on this page explains better than I could.

As for the "choose video mode", there was a vga= parameter, which isn't much used anymore and is deprecated; those instructions you link to are quite old.

  • BTW, so the grub bootloader switch to 32bit protected mode, and then do somethings, load kernel and back to real mode before give control to kernel? – Bình Nguyên Oct 31 '12 at 14:02
  • No. The bootloader passes control to the kernel which then enters the protected mode, where it stays (since the protected mode gives the kernel the features it needs). – Renan Oct 31 '12 at 14:03

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