Difference between amd quad-core a8 and i7

Desktop or Laptop?

Current i7 are intel and its based on sandybridge which got higher performance CPU per clock and high clock so high performance CPU wise. A8 got better intergrated graphic card but its not relavent if you got a graphic card and thats about as much as i know.
 
Are you asking about the laptop or the desktop parts?
A8-3500M = laptop A8-3850 = desktop part.

Core i7 also come in desktop or laptop CPUs.
Core i7 could be a dual core or quad core CPU. And there are some ultra low voltage Core i7 CPUs too.

You need the model numbers of the Core i7 and A8.