Just kind of wondering about Advanced Bloom

Hi, I’ve noticed that the Effect ‘Advanced Bloom’ can be a little bit intensive on the couple of systems I’ve tried it on, especially when the Blur parameter of the Effect is set to greater than 0.

I can see that it can be kind of demanding, but I was wondering if anyone knew what parts of the system it stresses most. Such as CPU or GPU, and if it’s GPU, if it has to do with the shader units, or some other part of the graphics card?