[OpenBIOS] Hello World

Pascal Dornier pdornier at pcengines.com
Wed Mar 11 11:48:30 CET 1998

>The MDA cards require absolutely no setup. They display text from the
>the power goes on. I suspect older [CEV]GA cards will be similar.

Not correct, you need to initialize the 6845 CRTC. Pardon the grotty

 ; Init Hercules card
 mov al,#$21 ;disable video
 mov dx,#$03b8
 out dx,al
 mov si,#herctext ;set text mode
 mov bl,#0
 mov dx,#$03b4
hercloop mov al,bl
 out dx,al
 inc dx
 cs: lods.b
 out dx,al
 dec dx
 inc bx
 cmp bl,#16
 jb hercloop
 mov al,#$29 ;enable video
 mov dx,#$3b8
 out dx,al
 mov ax,#$b000 ;clear screen
 mov es,ax
 mov ax,#vidfill
 mov cx,#2000
 mov di,#0
 rep stos
 jmp hercend
  ; Hercules text mode settings
herctext B $61,$50,$52,$0F,$19,$06,$19,$19  ; mode 7
 B $02,$0D,$0B,$0C,$00,$00,$00,$00

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