I had looked into performance of GC3, and was stumped as to why my 8 core AMD 8320 processor was only using 6 logical cores instead of 8. Others in fact with the same processor had stated they only had 4 logical processors being used for the game. Well, I was doing another overclock effort this evening, and I discovered something that apparently was causing the problem. This is probably trivial to those that already know this technique, but in the past I have used 'game booster' software to optimize, and however that was for single core games, and I was unaware this technique affected multi-core so much.
In Windows control panel, go to Power Settings and change it from the default 'balanced' setting to 'performance' setting. The last time I really tweaked this manually was in my winXP days, and well, quite a bit has developed since then. Performance will ensure that the processor is working at 100% speed at all times. It also seemed to solve my logical processor utilization issue. Now all 8 logical cores are being used. Unfortunately, I can't do an apples to apples comparison, as I really dont want to benchmark back on my original settings. As well, I'm tinkering with the worst case scenario of 100 factions (I'd like to start a thread to get some performance comparisons from the community), first dozen turns or so of turn duration took 34s, and now at turn 175, its up to about 50s.
Using the performance power profile, the Cores are no longer throttling down to lower speeds all the time, and with all cores being used, it certainly will give performance improvements. I certainly can state that I am visually seeing A LOT more utilization than I did before (cores 7 and 8 were always at < 5%). However, I can say that my electricity bill will be higher I certainly dont want to leave my PC on all day, doing nothing, with these settings.
When doing this, just make sure you are monitoring cpu temp, so you can prevent auto shutdown/locks, as your cpu temp will certainly increase a bit. Right now, I'm overclocking my 3.5GHz 8320 at 4.5GHz, with a cpu temp of 49C, and a socket temp of 57C, all fans on max.