You are right, I misremembered it. The e8400 didn't have hyperthreading. I guess the drawback of the q6600 with 4 cores was, it had lower speed at 2.4ghz compared to the 3ghz on the 8400. And that hurts a lot the single core performance, which is much more important for emulators. That's why you had this back and forth between both CPUs. I also didn't really understood all of that back then.