Then there's something wrong with either Firefox or your drivers; latest Chrome on a 4 year old machine (Windows 7 x64, Core i7, 12GB RAM) with a newer graphics

Then there's something wrong with either Firefox or your drivers; latest Chrome on a 4 year old machine (Windows 7 x64, Core i7, 12GB RAM) with a newer graphics card (GTX670) needs barely 10% CPU on a single core.