What makes a fast dog fast?

[BIG AL]

I have owned two Dog C's in my life and can't wait until I own another. One male and one female. Too bad I owned them 10 years apart and never got to breed them together. The male did not hunt very hard either but was a winder. I don't remember him ever going into a brushpile without a rabbit coming out of it. I could send him reluctantly into more but he knew he was wasting his time. Seemed like he could make a rabbit. The female hunted a little better and jumped her share but was not what I would call a jump dog. Both were very fast hounds that ran a good track and could run in any conditions. I have three hounds now that have noses that can smell a track that my other hounds can not. Frozen ground or hot dirt but none of these dogs are very fast. Maybe upper medium speed. I think that a good track running dog has to have a body made for speed, a good nose but I think they mostly need a good brain. Something is happening for these dogs in their head that is processing that track information at a faster rate. Like they have a Pentium 4 and those other dogs are stuck with old outdated processors.