Pc-98 Bios -

AH = 63h CX:DX = microseconds INT 18h (blocks) Get BIOS version

AH = 17h AL = rate (0–3Fh) INT 18h Set cursor position

AH = 72h INT 18h Returns: AX = bitmask (FDD count, display type, etc.) BIOS is slow but safe. For games/demos, bypass BIOS and access hardware directly. Common direct I/O ports (simplified): | Port | Purpose | |------|---------| | 0x60 | Keyboard data | | 0x61 | Keyboard control | | 0x66 | Display controller (GDC) | | 0x68 | CRTC address | | 0x6A | CRTC data | | 0xA0 | FDC status | | 0xA1 | FDC data | | 0x30 – 0x3F | Sound (YM2203/2608) | | 0x64 | Timer / interrupt mask |

AH = 24h AL = character (ASCII) BH = color (0–15, 0=black) INT 18h pc-98 bios

AH = 22h Returns: DH = row, DL = column

AH = 29h Returns: AL = current mode Reset disk system

AH = 11h INT 18h ZF = 1 if no key ZF = 0 if key waiting → AX = scancode/ASCII AH = 63h CX:DX = microseconds INT 18h

AH = 41h DL = drive CX = track number (0–79 for 2HD) DH = head (0 or 1) CH = sector number (1–8 for 2HD) AL = number of sectors ES:BX = buffer INT 18h Returns: CF = 0 if OK

MOV AX, 0xA000 MOV ES, AX MOV DI, 0 ; row 0, col 0 (character cell) MOV AL, 'A' MOV ES:[DI], AL But VRAM is planar: you must handle 4 planes for graphics. Prints "Hello" using BIOS INT 18h AH=24h:

AH = 70h INT 18h Returns: AX = BCD version (e.g., 0x0123 = v1.23) Prints "Hello" using BIOS INT 18h AH=24h: AH

AH = 28h AL = mode 0 = 80x25 text (16 colors) 1 = 80x28 text (400 lines) 2 = 640x400 graphics (4 planes) 3 = 640x400 graphics (16 colors) INT 18h

AH = 42h (same registers as read)

msg db 'Hello from PC-98 BIOS!', 0

AH = 40h DL = drive (0=A, 1=B, etc.) INT 18h Returns: CF = 0 if OK

AH = 62h CX:DX = microseconds between interrupts INT 18h