Why does SafeDisk screw with my game performance?

[GothicOne]

I have no performance issues with RTCW, America's Army, Unreal Tournament 2003, MechWarrior4, Morrowind, Star Trek Elite Force, all Rainbow Six series games. I own all of these titles and more and have no issues at 1600x1200 and have good to excellent FPS.

I bought IGI2 and can't even run it at 640x480. It is extremely jerky and jumpy outdoors and indoors and worse when I am near AI models. I grabbed a No CD patch for it and tada it plays perfectly smooth at 1280x1024x32.

My questions are...

In general why does SafeDisk screw with my game performance?

If Safe Disk (1 o r2) only checks the cd at the start up why does it continue to hinder performance?

I read that the multi-layered encrypted wrapper that secures the CD-ROM content runs ALL THE TIME. Can this be what is causing problems?

I need this information so I have something to fight back with. People on the game company forum do not believe that SafeDisk hurts performance.

Thanks for your help.