>existing system with a proposed new system. I'm going to try IB/Quadrics >because from what I can tell, the molecular dynamics applications that run >on the system will definitely take advantage of the faster interconnect. The devil is in the details when you say the code "can take advantage of" a faster interconnect. What the interconnect give you is an increase scalability (ie better parallel efficiency) as you increase the node count, rather than making it "go faster". When I last used gromacs in anger, (a few years ago) I was seeing pretty good parallel efficiency out to 4 machine (8 CPUs) on 100Mbit ethernet. There is no point in putting a fast interconnect between two machines; you won't see any better performance than if you'd just stuck an ethernet cross-over cable between them. If you are going to be running large simulations over more than 10 machines at a time, then yes, think about the interconnect, but benchmark first. Guy -- Dr. Guy Coates, Informatics System Group The Wellcome Trust Sanger Institute, Hinxton, Cambridge, CB10 1SA, UK Tel: +44 (0)1223 834244 ex 7199