Is it possible...?

[PsychoBastrd]

Is it possible to play PS2 backup without a modchip. ALL PS2 backups? Thanx

[Charlie]

No unless you perform the highly risky Knife/Cog swap trick to force the boot cd out at the right moment to swap your backup in.

Definition of modchip included key variants, but these don't do as comprehensive a job as soldered modchips.