I have a Sapphire R9 280x Toxic. Recently during games there is a small rectangle of lower dpi on my screen-on a 21 inch monitor this looks like about 1 1/2 x 1 1/2 inch. This is with both an HDMI cable and a DVI cable. Is this a typical symptom of bad memory, bad GPU, bad capacitors or what? Is there any way of testing the card to determine the source and potential fix for the problem?