I think one of the issues here is proving that one processor over an another gives better performance. Each turn on civ 4 is undefined and different due to the game being turn based.
You would need to compare 2 pcs with similar hardware such as graphics and memory but with a different cpu. If you overclock one cpu you overclock the other too. Even so you need the conditions to be realistic to run the games for several hours. How many people have liquid nitrogen at hand?
http://news.softpedia.com/news/Intel-Core-2-Duo-X6800-Overclocking-Record-5-3GHz-51236.shtml
(okay it didnt reach 8ghz but nice effort

)
I think the best method is to load a huge map around 2000ad on a huge map and see how long it takes to load the game and time between turns.
The trouble is comparing like for like and removing any bottlenecks such as memory or graphics.
Sticking in 4 gigs of ram and improving the graphics solved most of my game issues. A dying laptop may have also influenced these figures.
Thing with benchmarks is there is always one benchmark where the improvement of a new CPU doesnt always add over 3-5% difference. Where others you gain 30-40% at times.
ThuG OC Team Italy sets Overclock World Record Cedarmill 8.1 ghz
Now USE is tryin to get in back by goin even higher. This is faster then core2 when you do the 40% subtraction (btw very generous est. given today. Consider those org. estimates where taken from P4's running bottleneck on inefficient mobos and you can see here what happens when the core2 is made to share its mobo with the cedarmill 64mn lol )
quote from
this link
We here in Team NexGen are at Nexgen Consulting trying to break the world record right now, with (hopefully) a bit of help from koolance, and some LN2 or LHe4. We have a P5B deluxe, 631 cedarmill (ES), and 2 X 512MB Micron D9GKX Memory modules. So far we have hit 5.5ghz no problem but beyond 1.4v Vcore Air, water, and even our Prometeia Capped out under the heat load generated by the P4 631. But 4ghz at 1v was pretty cool. The use of Liquid Nitrogen is our best bet at breaking the 8179.89 MHz INTEL Pentium 4 631 (Cedar Mill) world record and bringing the title back to the good ole U.S.A.
Current World Record Held by "ThuG OC Team Italy"
IN case you don't know, the 'P4 631' they are tryin to break the record with is another cedarmill but with a better mobo and like you said, liquid nitro.
ALl ya have to do is check Ebay to see the number of bids and going prices for these pinnacle pent4's CPU's to understand a increasing amount of monocore players who believe including a 631 is part of winning performance plan (hella lot cheaper and fun to clock to!)
Part of it is OC is getting as acceptable to gen audiences as modding is to Civ4 fans . WIth new mobos and software like corecell, its gettin as easy as moddin civ3
YA I agree with all those complications using civ4 to compare cpu's.
Ive made the easy arguement (no counter arguement cept: " Im making the rules to cheat" from some
Campbell loop kid lol " ) to use civ3, at least as prilimary to take to the next level
IN fact this is what is going on when real lives sit down to get it on CPU vs CPU, for sure with a conroe. The last one never heard back from for some reason but mine still up on youtube
ANyway civ3 Is designed to rack up ever more tasks as in more of a stress test for the CPU (not ram or G-card BS)
I don't know about you but with my cedarmill playin 31 civs where each has 400 units fight all out ontop of massive (220x220) maps with 500 cities all full of calculations. Then you facter all that trading going on , oh did i say this was a mod with over double the varibles in categories at play (even twice the music lol) more luxuries goin round the same time , blah and blah.
You get the picture I presume. Civ World revolves round a cedarmill sun and simple, no dual or quadcore will outdo..I didn't say 'do' I said 'out do'
Thats the theory anyway, and with enough evidence to keep my money where my mouth is. It sure gets a lot of people fuming but in the ned they can't do anything there word < agaist mine and more numbers of equally unknowing Core 2 civfans don't make it any less true. Only a civ bench mark will do