Tim, the biggest change from a CPU perspective would be the removal of V=R and V=F support. See http://www.vm.ibm.com/perf/tips/z890.html for some background.
z/VM 5.2 did have significant changes in the area of memory management. However, since you were on a 31-bit addressing machine (9672) the benefits of that will not be significant, at least immediately. There would be some additional pathlength for z/VM 5.2 and the memory management (without any of the benefit). Most likely the new box will have more memory and perhaps you'll want to take advantage of that, in which case, the z/VM 5.2 would be preferable. Bill Bitner - VM Performance Evaluation - IBM Endicott - 607-429-3286
