I'm running DOSBox version 0.74 on Win7 64-bit with an Intel Core i7 CPU, and I'm very pleased with the performance.  I use a switch in the config file to get DOSBox to auto-attain max 100% CPU cycles, and set Frameskip to 5... there might be another flag or two that I tweak. I haven't tried the other runtime environments mentioned.

- Jason 

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Cheers from Mr. Tumnus!
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Hoofing it bare-chested since 1974.