I've been using this old thing for gaming and it's surprisingly able to keep up pretty well despite being over 8 years old... But for whatever reason when CPU load is sustained, at least one processor dives down to around 2.4ghz (sometimes both) and a big stutter accompanies this. I thought it was something to do with the R9 380 I put in taking too much power under load, but I replaced the 5770 I have and it's still doing the same thing. Basically if I bench the system, I'll get a universal good score if I bench single threaded. 1012 in CPUZ on Windows. But if I run the multicore test, it scores over 8000 for a few seconds, then quickly dives down and stutters around 3000. I've checked temps, forced the fans to run super fast just in case, run a much less power hungry video card, and basically did everything else I could trying to figure out the problem. Has anybody else had this problem with their older Mac Pro? Is this something I could fix by replacing the power supply or am I just better off building a dedicated gamer rig like a sane person? If it's not the power supply fizzling out I'm guessing it has to be an issue with the power delivery on the mainboard and if that's the case the whole system is toast to me.