I'm in the market for a new compute-heavy power desktop. I'm generally a machead (alu macbook, iphone, mac mini, bought the girlfriend a MBA etc) but I've never had a mac pro / powermac. My main use-case for the the computer will be to run several (many?) virtual machine images (predominantly linux) to act as a local server farm for dev and compute purposes. I'll probably also experiment with OpenCL (well, CUDA) programming. To-date, I've been looking at an Win7 rig, with a six-core i7 980X plus bells and whistles (SSD, nVidia 480 etc) - mainly because I can have exactly what I want and it's actually available now. However, I know I should really wait until the next Mac Pro is announced before making a £3000+ decision. To keep me pre-occupied until that magic moment when Apple deems us worthy enough for the 2010 edition, I was wondering what real-world examples of multiple VMs on a single Mac Pro people had. What's the maximum number you've got running concurrently? If you have them inter-communicating with each other, is there any significant bottlenecks? Presumably a 12GB Mac Pro would be adequate for running, say, five VMs? tl;dr: What's the most number of VMs you have running on your Mac Pro?