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

[Collins Chen]

Dear Ron,
     Yes, what you said is my current situation.

Collins







Ronald G Minnich <[EMAIL PROTECTED]> on 2002-03-01 13:51:35
                                                              
                                                              
                                                              
  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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On Fri, 1 Mar 2002, Collins Chen wrote:

>      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?
>

Collins, we need to summarize your current situation so I know what is
going on. I am getting mixed up.

I think you are trying to make linuxbios execute 16-bit code. You have
added code to linuxbios to try to switch to 16-mode and call the vga bios
to turn on vga.

I think the problem you are having is you do not have a proper GDT.
linuxBIOS does not set up 16-bit GDT entries. There is no room. Even if
you did have proper GDT entries, you have not loaded ds,ed,fs,gs with the
right segment values, and you have not done a long jump to set cs to
16-bit segment.

If you can wait until monday I can send you some code. Sorry I have been
so quiet, I am on travel the last 10 days.

Does this make sense?
ron