well, when the TI ROM is loaded on the calc (like an upgrade) it has a checksum that is read by the boot loader, it is also in 512bit RSA encryption. (ahhhh!) So in order for us to write a new ROM on the calc we have to get past the encryption or something ( i dont completely understand it myself ). If our ROM's check sum isn't correct for the boot loader, than it will not load our ROM -kyle