Actually, a small AWS image comes with 1.7GB of RAM. That's a big difference. In terms of the processor metric, that's harder to gauge. Right now, Amazon say

Actually, a small AWS image comes with 1.7GB of RAM. That's a big difference. In terms of the processor metric, that's harder to gauge. Right now, Amazon says one EC2 compute unit is roughly equivalent to a 1.0-1.2GHz 2007 Xenon or Opteron (or a 1.7GHz 2006 Xenon which was their original documentation). Think of it this way, Amazon is putting you on a beefy server with some other people. I'd guess these servers are 4-core boxes running at around 2GHz+ with 16GB of RAM. So, with the Extra-Large instance, you're basically getting the box (15GB of RAM, 4 cores with 2 compute units per core (roughly 2-2.4GHz per core)). So, with the Large instance, you're getting half of the server (2x 2GHz Xenon processors) and with the small instance you're probably getting one core at half speed. And that's really as much as most people will need especially since I'm guessing there's a bit of bursting ability to the CPU capacity. Hope that helps make Amazon's CPU situation a little more understandable.