RHEL5 always uses a Linux Timer Rate timer rate of 1000 Hz. This can be decreased in RHEL5.1 for greater efficiency of RHEL SMP guests.
RedHat has not enabled VMI in their kernels, so out-of-the-box paravirtualization is not possible. But custom kernels can easily be built to take advantage of this feature. See VMware KB article #1003644.
