VGA_GC_MODE
reg[4] = vga_get_grc(VGA_REG_BASE, VGA_GC_MODE);
vga_set_grc(VGA_REG_BASE, VGA_GC_MODE, 0x00);
vga_set_grc(VGA_REG_BASE, VGA_GC_MODE, reg[4]);
REG_WRITE1(sc, VGA_GC_ADDRESS, VGA_GC_MODE);
REG_WRITE1(sc, VGA_GC_ADDRESS, VGA_GC_MODE);
REG_WRITE1(sc, VGA_GC_ADDRESS, VGA_GC_MODE);