As long as it's running the same set and configured the same then cpu is likely to be the culprit there, a 20% drop is pretty high though. Tekken 3 defaults to interlace mode, and I don't get 100% when it's running in interlace. It runs much quicker if you disable interlace in test mode (forgetting that you disabled interlace but now it's enabled is a common reason that people notice speed drops).
It could be graphics drivers, but it would have to be doing something drastically wrong (which is possible).
Of course this is all based on standard settings, if you have vsync/triple buffering enabled etc then they can affect timing in strange ways depending on your config.
Testing with no mame.ini and just specifying the options you need on the command line is useful.
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Re: Mame Performance XP 64bit Vs Windows 7 64bit
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