Sudden drop in performance

[TheAtomicNord]

First off, thank you all for your responses.

Here are the pictures of my settings as requested: http://imgur.com/a/LoAzx

I am using the geforce 335.23 drivers which are the latest available ones.

The driver is set to prefer maximum performance.

GPU-Z reports that my card is running at a constant 1006 MHz at 34 degrees Celsius.

I'm running both versions of dolphin. The dev version is a little faster, but more unstable. The normal version runs at a stable (ish) 20fps.

Thanks again for all your help