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Could I just switch to real mode every time I wanted to print a message or would it be easier to print a message in protected mode?

You mean like this :

mov ax, 0B800h
mov gs, ax
mov byte [gs:0], '1'

I use this for debuging pmode to see if it worked.
Could I just use this and just change the '1' to my message?

printmsg:
 mov ax,0B800h 
 mov gs,ax
 mov di,message
 mov cl,byte[ds:di]
 mov byte[gs:si],cl
  inc di
  inc si
 cmp cl,0
 jne printmsg

message db 'frank test 1,2,3'

Code: Select all

mov  ax, 0B800h
mov  gs, ax
mov  byte [gs:0], '1'

mov ax, 10h     ; check your GDT for the number to use
mov gs, ax
mov [gs:0B8000h], '1'

beyondsociety wrote: This is wear my logic is coming from but thanks for showing me what the selector for gs is.

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I will assume that your early pmode code does not use GS, and that your display is in text mode and that your display buffer is at B8000. Put the following code well before you switch to pmode:

mov ax, 0B800h
mov gs, ax
mov byte [gs:0], '1'

Now take lines like these:

mov byte [gs:2], '2'
mov byte [gs:4], '3'
mov byte [gs:6], '4'
etc.

and distribute them through the following code. DO NOT WORRY about the fact that GS has a selector that is incompatible with pmode. DO NOT load a pmode compatible selector into GS (until you are sure your GDT etc. work well enough that you probably don't need this debugging aid anymore anyway).