CR53
unsigned char CR50, CR51, CR53, CR55, CR58, CR5B, CR5D, CR5E;
reg->CR53 = 0x00;
vga_out8(0x3d5, reg->CR53 & 0x7f, par);
vga_out8(0x3d5, reg->CR53, par);
reg->CR53 = vga_in8(0x3d5, par);
vga_out8(0x3d5, reg->CR53, par);