What is the scientific explanation why we need mod chips?

[thewessman]

I have a little bit of understanding about the reason for modchips. If I understand it correctly, the media (cd, dvd) has some sort of data on itself that tells the game console that it is a legitimate piece of software. If that is the case, then why is that data unrecordable, why can't software copy that data over to another media, especially when doing a 1:1 copy?? I understand that a modchip bypasses the cpu's authentication process either by giving the cpu false authentication data, or simply by ignoring it all together. The question still remains, however, why can't an exact backup, be an exact backup?! Are the reading devices simply not capable of reaching the data sector, and if so, how come the readers in the consoles are able to? If we were able to make a true 1:1 copy, then the recorded media should be identical to the original, but since we must use modchips, then it is safe to assume that the copies are really a 1:.999 ratio.