So, it looks like I’m not the only one trying to figure out Amazon EC2 virtual CPU allocation. Slashdot runs the story (and a heated debate, as usual) on the subject of Amazon’s non-definitive virtual CPUs:
ECU’s were not the simplest approach to describing a virtual CPU, but they at least had a definition attached to them. Operations managers and those responsible for calculating server pricing could use that measure for comparison shopping. But ECUs were dropped as a visible and useful definition without announcement two years ago in favor of a descriptor — virtual CPU — that means, mainly, whatever AWS wants it to mean within a given instance family.
A precise number of ECUs in an instance has become simply a “virtual CPU.”