We investigated the sensitivity of Advanced Performance Algorithm (APA) which was installed in KLA351. It was found that the sensitivity of APA was much better than that of P1831 which was previously installed in KLA351. 1 GDRAM reticles were inspected by APA successfully while we could not achieve it with P1831. HOwever, APA has still some issues as follows: (1) Missing some kinds of defects when tested with our sensitivity test reticle. (2) Falling short of the sensitivity requirement for 1 GDRAM reticles fabrication. We should also report that there are some issues which are deeply related to the reticle fabrication process, because we have recognized again that the possibility of inspection algorithm depends on pattern edge roughness which comes from the reticle fabrication process.