add comment / corrections

build.bat

@@ -4,4 +4,4 @@ cd src
 "c:\program files\NASM\nasm" -f bin boot.asm -o ..\build\bios.bin
 cd ..
 
-qemu-system-x86_64 -bios build/bios.bin -device loader,file=build/vgabios.bin,addr=0xC0000,force-raw=on -device isa-debugcon,chardev=myconsole -chardev stdio,id=myconsole -k be -display sdl
+qemu-system-x86_64 -bios build/bios.bin -device loader,file=roms/vgabios.bin,addr=0xC0000,force-raw=on -device isa-debugcon,chardev=myconsole -chardev stdio,id=myconsole -k be -display sdl

src/bda.asm

@@ -1,6 +1,31 @@
+; =============================================================================
+;  Project  : Custom BIOS / ROM
+;  File     : bda.asm
+;  Author   : frater
+;  Created  : 06 jan 2026
+;
+;  License  : GNU General Public License v3.0 or later (GPL-3.0+)
+;
+;  This program is free software: you can redistribute it and/or modify
+;  it under the terms of the GNU General Public License as published by
+;  the Free Software Foundation, either version 3 of the License, or
+;  (at your option) any later version.
+;
+;  This program is distributed in the hope that it will be useful,
+;  but WITHOUT ANY WARRANTY; without even the implied warranty of
+;  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;  GNU General Public License for more details.
+;
+;  You should have received a copy of the GNU General Public License
+;  along with this program.  If not, see <https://www.gnu.org/licenses/>.
+;
+; =============================================================================
+
+
 ;
 ; https://wiki.nox-rhea.org/back2root/ibm-pc-ms-dos/hardware/informations/bios_data_area
 ;
+
 %define BDA_SEGMENT						0x0040							; segment BDA
 
 ; custom var

src/boot.asm

@@ -1,37 +1,56 @@
+; =============================================================================
+;  Project  : Custom BIOS / ROM
+;  File     : boot.asm
+;  Author   : frater
+;  Created  : 06 jan 2026
 ;
+;  License  : GNU General Public License v3.0 or later (GPL-3.0+)
 ;
+;  This program is free software: you can redistribute it and/or modify
+;  it under the terms of the GNU General Public License as published by
+;  the Free Software Foundation, either version 3 of the License, or
+;  (at your option) any later version.
 ;
+;  This program is distributed in the hope that it will be useful,
+;  but WITHOUT ANY WARRANTY; without even the implied warranty of
+;  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;  GNU General Public License for more details.
 ;
+;  You should have received a copy of the GNU General Public License
+;  along with this program.  If not, see <https://www.gnu.org/licenses/>.
+;
+; =============================================================================
+
 BITS			16
 org				0
 
+; ---------------------------------------------------------------------------
 ;
 ; configuration du bios
 ;
+; ---------------------------------------------------------------------------
 %define DEBUG_PORT		0xe9								; 0x402 ou 0xe9
 
-%define VIDEO_SEG    	0xB800        			; ou 0xB000
-%define VIDEO_ATTR   	0x07
 
 ; initial stack 
-%define STACK_SEG   	0x0030
+%define STACK_SEG   	0x0030							; compatible avec le BMM (Bios Memory Maps)
-%define STACK_TOP    	0x0100        			; choix commun en RAM basse (pile descend)
+%define STACK_TOP    	0x0100        			; choix commun en RAM basse (pile descendante)
 
 %define MEM_SEG_DEB		0x0800 						  ; 0x0800:0000 = 0x8000 (32KB) évite IVT/BDA + stack 7C00
 %define MEM_SEG_END   0xA000    					; 0xA000:0000 = 0xA0000 (début zone vidéo)
 %define MEM_SEG_STEP  0x0040    					; 1KB = 0x400 bytes = 0x40 paragraphs
 
+
+
+						jmp				reset								; ce jump n'est pas sensé être executer, il est présent uniquement pour le debug
+
 ; definition du BDA
 %include 		".\bda.asm"
 
-
-						jmp				reset
-
 %include 		".\drivers\debug.asm"
 %include		".\drivers\gfx_cgam.asm"
 %include		".\drivers\mouse_ps2.asm"
 
-err_novga		db 				'No VGA Card BIOS',0
 err_vganok	db				'VGA Not Initialized',0
 err_end			db				'code completed successfully',0
 
@@ -74,10 +93,10 @@ endless:		nop
 						jmp				endless
 						
 ; ---------------------------------------------------------------------------
-; Détection les ROM supplementaires
+; Test si le vecteur INT 10h à été modifié (par la ROM)
-; Teste la RAM de 0xC000 jusqu’à 0xE000, par pas de 2KB.
 ;
-; Si une ROM est détectée, le code de la ROM sera appelé.
+; Si le vecteur n'a pas été modifiée, on considère que la ROM video n'a pas
+; été chargée.
 ; ---------------------------------------------------------------------------	
 setup_check_vga:
 						; vérification de l'offset 0x0000:0x0040 qui DOIT etre différent de @default_isr
@@ -91,12 +110,11 @@ setup_check_vga:
 						; Comparer avec default_isr (offset) et CS (segment)
 						mov 			dx, default_isr 		; DX = offset default_isr (dans notre CS)
 						cmp 			bx, dx
-						jne 			.init_ok						; interrupt different
+						jne 			.init_ok						; vecteur different, bios initialisé
 						cmp 			cx, ax
 						jne 			.init_ok
 						
-						; no VGA init
+						mov				ax,cs								; vecteur identique, sans doute pas d'initialisation
-						mov				ax,cs
 						mov				ds,ax
 
 						mov				si, err_vganok
@@ -112,7 +130,6 @@ setup_check_vga:
 ; ---------------------------------------------------------------------------						
 setup_load_rom:						
 						mov 			bx, 0xC000
-						mov				al,'*'
 .scanloop:
 						mov 			ds, bx
 						cmp				word[0x0000],0xAA55	; ROM signature
@@ -133,20 +150,11 @@ setup_load_rom:
 						add				bx, 0x80						; add 2kb
 						cmp 			bx, 0xE000
 						jbe 			.scanloop
-						
-						cmp				al,'.'
-						je				.end
-						; no rom found :
-						mov				bx,cs
-						mov				ds,bx
-
-						mov				si, err_novga
-						call			debug_puts
 .end:						
 						ret
 
 ; ---------------------------------------------------------------------------
-; Détection RAM conventionnelle (8088, BIOS maison) — sans BIOS
+; Détection RAM conventionnelle 
 ; Teste la RAM de MEM_SEG_DEB jusqu’à 0xA000 (640KB), par pas de 1KB.
 ; Méthode: sauvegarde 1 mot, écrit 2 patterns, relit, restaure.
 ;
@@ -217,9 +225,6 @@ setup_ram:
 
 ; ---------------------------------------------------------------------------
 ; IVT install (8088, mode réel) - remplit les 256 vecteurs avec un handler IRET
-; Hypothèses:
-; - code en ROM (CS typiquement = 0xF000), handler réside dans ce même segment
-; - interruptions désactivées (CLI) pendant l'installation
 ; ---------------------------------------------------------------------------
 setup_ivt:
 						; installation de la table d'interrupts

src/drivers/debug.asm

@@ -1,4 +1,25 @@
-
+; =============================================================================
+;  Project  : Custom BIOS / ROM
+;  File     : debug.asm
+;  Author   : frater
+;  Created  : 06 jan 2026
+;
+;  License  : GNU General Public License v3.0 or later (GPL-3.0+)
+;
+;  This program is free software: you can redistribute it and/or modify
+;  it under the terms of the GNU General Public License as published by
+;  the Free Software Foundation, either version 3 of the License, or
+;  (at your option) any later version.
+;
+;  This program is distributed in the hope that it will be useful,
+;  but WITHOUT ANY WARRANTY; without even the implied warranty of
+;  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;  GNU General Public License for more details.
+;
+;  You should have received a copy of the GNU General Public License
+;  along with this program.  If not, see <https://www.gnu.org/licenses/>.
+;
+; =============================================================================
 
 debug_puts:
 .next:

src/drivers/gfx.asm

@@ -1,3 +1,27 @@
+; =============================================================================
+;  Project  : Custom BIOS / ROM
+;  File     : boot.asm
+;  Author   : frater
+;  Created  : 06 jan 2026
+;
+;  License  : GNU General Public License v3.0 or later (GPL-3.0+)
+;
+;  This program is free software: you can redistribute it and/or modify
+;  it under the terms of the GNU General Public License as published by
+;  the Free Software Foundation, either version 3 of the License, or
+;  (at your option) any later version.
+;
+;  This program is distributed in the hope that it will be useful,
+;  but WITHOUT ANY WARRANTY; without even the implied warranty of
+;  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;  GNU General Public License for more details.
+;
+;  You should have received a copy of the GNU General Public License
+;  along with this program.  If not, see <https://www.gnu.org/licenses/>.
+;
+; =============================================================================
+
+
 %define GFX_MODE			0x06								; MCGA HiRes (B/W)
 %define GFX_WIDTH			640
 %define GFX_HEIGHT		200

src/drivers/gfx_cgam.asm

@@ -1,6 +1,31 @@
+; =============================================================================
+;  Project  : Custom BIOS / ROM
+;  File     : gfx_cgam.asm
+;  Author   : frater
+;  Created  : 06 jan 2026
 ;
-; graphics drivers for CGA 640x200x2
+;  License  : GNU General Public License v3.0 or later (GPL-3.0+)
 ;
+;  This program is free software: you can redistribute it and/or modify
+;  it under the terms of the GNU General Public License as published by
+;  the Free Software Foundation, either version 3 of the License, or
+;  (at your option) any later version.
+;
+;  This program is distributed in the hope that it will be useful,
+;  but WITHOUT ANY WARRANTY; without even the implied warranty of
+;  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;  GNU General Public License for more details.
+;
+;  You should have received a copy of the GNU General Public License
+;  along with this program.  If not, see <https://www.gnu.org/licenses/>.
+;
+; =============================================================================
+
+;
+; graphics drivers pour carte video/mode CGA-Mono (640x200x2)
+;
+%define VIDEO_SEG    	0xB800        			; ou 0xB000
+
 %define GFX_MODE			0x06								; MCGA HiRes (B/W)
 %define GFX_WIDTH			640
 %define GFX_HEIGHT		200
@@ -9,8 +34,12 @@
 %define CGA_ODD_BANK  0x2000
 %define BG16_SIZE     48
 
-; ce mode est entrelacé, un bit/pixel, 8 pixels par octet
 
+; ------------------------------------------------------------
+; initialise le mode graphique (via l'int 10h)
+; 
+; ce mode est entrelacé, un bit/pixel, 8 pixels par octet
+; ------------------------------------------------------------
 gfx_init:
 						; init graphics mode
 						mov 			ah, 0x00     			; AH=00h set video mode
@@ -21,17 +50,72 @@ gfx_init:
 
 						ret
 
-; PutPixel(x=cx, y=dx, color=al) sur page bh
+; ------------------------------------------------------------
+; Dessine un pixel, accès VRAM direct.
+;
+; In:
+;   CX = x (0..639)
+;   DX = y (0..199)
+;   AL = color (0=black, !=0=white)
+;
+; ------------------------------------------------------------
 gfx_putpixel:
-						mov  			ah, 0Ch
+						push	    bx
-						;mov  			al, 0Fh       ; couleur (0..15)
+						push  	  di
-						;mov  			bh, 00h       ; page
+						push    	es
-						;mov  			cx, 100       ; x
+
-						;mov  			dx, 50        ; y
+						mov	     ax, VIDEO_SEG
-						int  			10h
+						mov 	    es, ax
+
+						; DI = (y>>1)*80 + (x>>3) + (y&1)*0x2000
+						mov 	    bx, dx
+						and   	  bx, 1                      ; BX = y&1
+
+						mov	  	  ax, dx
+						shr	    	ax, 1                      ; AX = y>>1
+						mov 	   	di, ax
+						mov 	    ax, di
+						mov   	  di, CGA_STRIDE
+						mul     	di                         ; DX:AX = (y>>1)*80
+						mov 	    di, ax
+
+						test  	  bx, 1
+						jz      	.bank_ok
+						add  		  di, CGA_ODD_BANK
+.bank_ok:
+						mov  		  ax, cx
+						shr  		  ax, 3                      ; AX = x>>3
+						add  		  di, ax
+
+						; masque bit = 0x80 >> (x&7)
+						mov     	bl, cl
+						and     	bl, 7                      ; BL = x&7
+						mov     	ah, 080h
+						mov     	cl, bl
+						shr     	ah, cl                     ; AH = bitmask
+
+						; write
+						cmp  	   	al, 0
+						je    	  .clear
+
+.set:
+						or   		  byte [es:di], ah
+						jmp       .done
+
+.clear:
+						not       ah
+						and       byte [es:di], ah
+
+.done:
+						pop 	    es
+						pop   	  di
+						pop     	bx
 						ret
 
-; draw background pattern
+; ------------------------------------------------------------
+; Dessine un background "check-board", accès VRAM direct.
+;
+; ------------------------------------------------------------
 gfx_background:
 						mov				ax,VIDEO_SEG
 						mov				es,ax

src/drivers/mouse_ps2.asm

@@ -1,5 +1,29 @@
+; =============================================================================
+;  Project  : Custom BIOS / ROM
+;  File     : mouse_ps2.asm
+;  Author   : frater
+;  Created  : 06 jan 2026
 ;
-; controlleur de souris via le i8042 (PC Classique)
+;  License  : GNU General Public License v3.0 or later (GPL-3.0+)
+;
+;  This program is free software: you can redistribute it and/or modify
+;  it under the terms of the GNU General Public License as published by
+;  the Free Software Foundation, either version 3 of the License, or
+;  (at your option) any later version.
+;
+;  This program is distributed in the hope that it will be useful,
+;  but WITHOUT ANY WARRANTY; without even the implied warranty of
+;  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;  GNU General Public License for more details.
+;
+;  You should have received a copy of the GNU General Public License
+;  along with this program.  If not, see <https://www.gnu.org/licenses/>.
+;
+; =============================================================================
+
+
+;
+; controleur de souris via le i8042 (PC Classique)
 ;
 
 %define	PS2_PORT_BUFFER		0x60

src/drivers/textmode.asm

@@ -1,3 +1,26 @@
+; =============================================================================
+;  Project  : Custom BIOS / ROM
+;  File     : textmode.asm
+;  Author   : frater
+;  Created  : 06 jan 2026
+;
+;  License  : GNU General Public License v3.0 or later (GPL-3.0+)
+;
+;  This program is free software: you can redistribute it and/or modify
+;  it under the terms of the GNU General Public License as published by
+;  the Free Software Foundation, either version 3 of the License, or
+;  (at your option) any later version.
+;
+;  This program is distributed in the hope that it will be useful,
+;  but WITHOUT ANY WARRANTY; without even the implied warranty of
+;  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;  GNU General Public License for more details.
+;
+;  You should have received a copy of the GNU General Public License
+;  along with this program.  If not, see <https://www.gnu.org/licenses/>.
+;
+; =============================================================================
+
 ;
 ; text mod functions
 ;