SR12
unsigned char SR10, SR11, SR12, SR13, SR15, SR18, SR29, SR30;
reg->SR12 = (r << 6) | (n & 0x3f);
vga_out8(0x3c5, reg->SR12, par);
reg->SR12 = vga_in8(0x3c5, par);
vga_out8(0x3c5, reg->SR12, par);