I'm running DOSBox 0.74 on Xubuntu 12.10 64-bit, and have run into some serious performance issues.

My CPU is an i5-3210M, but I'm only getting about 30 fps in the Quake timedemos. I've seen slower machines get 100+ fps. Other games are running sluggishly as well.

My DOSBox config file is more or less stock. Any ideas as to what might be causing this? (I'm tempted to blame the 64-bit OS, but that's just a wild guess.)