[charlie_ps2]

Guess what? Here's the answer.

On the pressed disks Sony have placed a coded sequence of wobbles in the data groove. These yield a tracking error that is picked up in the firmware. Before correcting for the tracking error (which is within re-read boundaries), the deviation is noted and stored in proprietary Sony code. The sequence is all in the boot area and the decoding algorithm provides the region code for that game which is then checked for red Screen purposes.

When you put the disk through the CD or DVD reader on the way to burning, the tracking error is automatically corrected and you get a result devoid of the wobble in the groove. You can't replicate the tracking error. So you get a red screen unless a mod-chip intervenes and gets round that.

Sony have patented this technique and it took a trawl of their patents to come to this conclusion.

So there.