Except as usual, Taz is talking rubbish, because at the moment and probably for a significant amount of time, your light guns won't work in Vista. There are some very serious driver problems and no plans by manufacturers to update them right now.
So it's more than a bit pointless being able to run it at full speed in there if you cant actually play it in there.
Lets see MAME 32bit 0.123u3 Windows XP Pro 32bit benchmarks for Carnevil:
224.36% (190% in game actual)@ 4.4ghz DDR2-980
122.18% (104% in game actual)@ 2.4ghz DDR2-800
Oh look at that!, I was right a 2.4ghz Core 2 Duo can run carnevil without issue, guess Fozzy The Bear is wrong as usual. Though looking at those benchmarks I would suggest 2.6ghz to be safe if your running mame 32bit on XP for the light gun support.
Since the topic has been brought up, there is a solution for those wanting a light gun that works in Windows Vista in the form of the Nintendo Wiimote, you need a USB bluetooth dongle, Wiimote,Wiimote lightgun adaptor, Sensor bar (Wii Light bar), and GlovePie software to make this work. I haven't yet tested this myself because I only did the research on it last weekend, but a quick search on google or youtube turns are plenty of working examples of the Wiimote working as a mouse in Vista, which is one very short step to being used as a light gun in M.A.M.E. , I will in time test this for myself and post the result here if someone doesn't do it first.
Fozzy, no one asked about lightgun support, they asked about Carnevils preformance and based on the fact I've benchmark that ROM probably over a hundred times now, I feel that I was qualified to give advice as to want is required to run it a full speed, I used the a Vista 64bit benchmark score because it was what I had handy and was most current, and then scaled that score with a safety margin to where people are more likely to be running their system. I've yet to see you make a postive contribution to this forum, all your posts seem to consist of attacking others for having Ideas that are not your own, or stating your opinion over and over no matter how irrelavant the opinion is to the topic at hand, in what appears to be the pathetic hope that someone will take you opinion as fact. Get over yourself, and come up with some real and relevant facts next time before you try attacking me. (At this point I'm sure you will ignore all the facts at hand and instead reply with a personal attack of some form or something equal irrelavent to this thread.)