Re: Why CPU don't execute 16-bit code

[Collins Chen]

Dear Ebiederman,
     As you said, The procedore is:
          From 32bit protected mode
          Switch to 16bit protected
          Switch to 16bit real mode.
Is that said I can load a new 16bit GDT even in 32bit protected mode? Thanks!

Collins







[EMAIL PROTECTED] (Eric W. Biederman) on 2002-03-01 13:53:16
                                                              
                                                              
                                                              
  To:          Collins Chen/ALI_ZSZ/ACER@ACER                 
                                                              
  cc:          Konstantin Zhidkov <[EMAIL PROTECTED]>,   
               [EMAIL PROTECTED]                             
                                                              
                                                              
                                                              
  Subject      Re: Why CPU don't execute 16-bit code          
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"Collins Chen" <"collins_chen"@ali.com.tw> writes:

> Dear Konstantin,
>      I guess maybe the GDT in "start32.inc" cause my switchingreal mode code
> invalid. If some bit in GDT will be limitative to switching protected mode to
> real mode?

Add into the descriptor a 16 bit code segment.

The procedore is:
>From 32bit protected mode
Switch to 16bit protected
Switch to 16bit real mode.

And of course freebios/tools/mkelfImage/elf32-i386/head.S already
has code to do this.

Eric