What do you mean? Dou you want to know how many separate app server instances you can run? If so, that all depends on your system (how much memory do you have is usually the biggest issue) and how bust each instance will be.
If your app server instances are really busy, I usually recommand 2GB per instance. Also I usually recommend a NIC for every two instances. Additionally, you might want to allocate 1 or 2 CPUs per instance (that is, on a 4 core system run at most 4 instances).
If the app server instances are not busy, you can use less memory and allocate more instances per CPU.