I am running the Moogerfooger Ring Modulator on a Mac Book Pro that has a 2.2 Ghz Intel Core 2 Duo processor and 4 GB of RAM. I run the plug-in in Pro Tools LE 7.4 that runs with a Digi 002R audio interface. The plug-in runs great on this system as I have never had a problem running it. I've only really used one or two of these at a time, being that it is a unique effect and I never end up needing or wanting it on too many things.
I've had this Ring Modulator plug-in for about a year and it is my only Ring Mod plug-in. You can get some pretty crazy sounding effects from this, and if you are looking at this, you probably have an idea about what it does. It is a cheap solution for me because while I like the effects this produces, I don't use it often enough to warrant getting a hardware based Ring Modulator. This is modeled after the Moogerfooger pedal of the same name and does a pretty good job of reproducing it - both in look and in sound. It splits the signal to produce new unique sound and has all of the parameters you would want on a ring modulator. It is easy to get a wide variety of interesting sounds and is definitley worth picking up if you want the sounds a Ring Modulator makes without any big price tag.