RealTemp and the plugin use high performance timers within Intel Core based CPUs to calculate the load percentage. During testing, this method seems to respond quicker and more accurately than Task Manager does. If you run a single threaded task on a Quad core processor, that task gets scheduled and moved around from core to core approximately 300 times per second. I don't think the method that the Task Manager uses is fast enough to accurately monitor that. The only accurate way is to use the Intel high performance timers. They were specifically designed for this type of monitoring. When testing you need a very constant load on the CPU. I use Prime95 Small FFTs for this. Here's how my chart looks. On my Q6600 I started out using 1 thread of Prime Small FFTs, then 2, 3, 4, 0, 2 and then back to 1. The top overall load graph looks exactly what you would expect it to look like. The data for this overall graph comes from reading each individual core and then averaging those 4 values out. With the RivaTuner plugin, you can go to any spot on the graph and the 4 individual loads will always average out and exactly equal the total load. If this plugin was totally wrong, there's no way that the top graph would be so smooth and accurately reflecting the load being created by Prime95 when the individual load of each core is jumping around so rapidly. My opinion is that during rapid load transitions which is any time a CPU is partially loaded, the Task Manager method of calculating that load tends to over react to what's really going on inside an Intel CPU. It's impossible for the plugin to be 100% accurate during Prime testing but for this same method based on Intel's high performance timers to be totally wrong during your light load testing. Personally, I'd trust the plug-in before trusting Task Manager. The Task Manager method dates back quite a few years and is too slow to accurately reflect the true load on each core of a CPU. Here's the latest beta of RealTemp which includes the plugin for anyone that needs it: http://www.fileden.com/files/2008/3/3/1794507/RealTempBeta.zip Edit: Try running 1 and then 2 threads of Prime95 Small FFTs to see how accurate the plugin looks on your computer.