I don't much about RedHat, but came across this paper. It might be of help or not?
Red Hat Tuning rhel4_vm.pdf
Some OS's will make assumptions about how the machine is going to be used based upon amount of memory that it finds upon installation which of course may or not be what you want to have happen. The more physical memory you have, the more complex the virtual memory table become. Anyway this article sounded relevant to your problem. And you can compare between your two different machines. It possible that the box with more memory will require different settings. Sounds like some experimentation is going to be required. Sounds like we are all curious as to what you find out!
