VGA_AC_MODE_CONTROL
atr = vga_get_atr(VGA_REG_BASE, VGA_AC_MODE_CONTROL);
vga_set_atr(VGA_REG_BASE, VGA_AC_MODE_CONTROL, atr);
val = vga_get_atr(VGA_REG_BASE, VGA_AC_MODE_CONTROL);
vga_set_atr(VGA_REG_BASE, VGA_AC_MODE_CONTROL, val);
reg[6] = vga_get_atr(VGA_REG_BASE, VGA_AC_MODE_CONTROL);
vga_set_atr(VGA_REG_BASE, VGA_AC_MODE_CONTROL, reg[6]);
REG_WRITE1(sc, VGA_AC_WRITE, VGA_AC_MODE_CONTROL);
REG_WRITE1(sc, VGA_AC_WRITE, VGA_AC_MODE_CONTROL);