Intel had JUST introduced the first dual core cpu when I bought this machine, and there was some talk of poor floating point operations with it. So, I went with the 3.6 Ghz single core chip instead. In retrospect, that was probably a mistake. Oh, well! I understand you have to get an extra node license if you're running dual-core cpu's with C5 Pro?? Hmmm... I'm not sure you're really getting TWICE the performance with dual-core. I seem to recall hearing 30-50% increases were about average with multi-threaded code. What do extra node licenses for C5 Pro cost??