Just thought Id post my results as I just built a new Core 2 Duo computer.
I only ran a few games, in a very small sample. And while I snagged my arguments from
http://benchmark.mameworld.net/ once I had started I realized I should have used a longer sample time. Blitz 2k for instance, never gets to the actual gameplay. Oh well. So take these numbers for what they are worth, at the very least, a comparative example between OS's and clock speeds.
All binaries were the official binaries. Settings were:
mame -noautoframeskip -frameskip 0 -seconds_to_run 100 -nothrottle -nosleep -video ddraw -skip_gameinfo -effect none -nowaitvsync -noreadconfig -mt ROMNAME
I also saw about 5% increase due to multithreading across the board as mentioned earlier in this thread.
Old PC - Athlon XP 1700 - mame.exe
Killer Instinct 2 - 84.6%
Cruisin USA - 83.9%
Gauntlet Dark Legacy - 24.0%
Blitzk 2k - 25.3%
Gradius 4 - 17.9%
New PC in 32bit XP - 2.66ghz - mame.exe:
Killer Instinct 2 - 352.9%
Cruisin USA - 149.3%
Gauntlet Dark Legacy - 86.4%
Blitz 2k - 100.9%
Gradius 4 - 74.3%
New PC in 32bit XP - 2.66ghz - mamepp.exe:
Basically the same as mame.exe
New PC in 32bit Vista - 2.66ghz - mame.exe:
Basically the same as XP.
New PC in 64bit Vista - 2.66ghz - mame.exe:
Basically the same as 32bit.
New PC in 64bit Vista - 2.66ghz - vmame64.exe:
Killer Instinct 2 - 430.5%
Cruisin USA - 175.3%
Gauntlet Dark Legacy - 97.8%
Blitz 2k - 126.4%
Gradius 4 - 49.2%
Overclocked PC in 64bit Vista - 3.33ghz - vmame64.exe:
Killer Instinct 2 - 538.1%
Cruisin USA - 217.8%
Gauntlet Dark Legacy - 119.1%
Blitz 2k - 157.3%
Gradius 4 - 61.9%
Gradius is much slower in the 64 bit binary, but the other 4 games I tested saw anywhere from 5-20% speed increase, just by going 64 bit. So my assertion if you get a core 2 duo, get a 64 bit OS, and get rockin.