This is not correct... PSX/PS2 modchips have never used Sony BIOS to accomplish protection defeating; they modify the protection data as it is transmitted across the system bus.
The gamecube mod that exists is also a microcontroller mod.
Xbox is only a copyright infringement case because they are using a cracked BIOS to defeat the copy protection. Not that anyone is selling the chips with the code on it, but because they are apparently marketing the blank flash devices for that purpose.
Score:2, Informative