My head has been playing with the difference between core 2 duo (older) and core i3. Then, I start exploring Intel website and find what i3, i5 i7 are all about.
In this post, I simply compare this two processors. I referred to the site on core 2 duo and core i3 specification. Both are similar in term of processor number (2 cores).
The main differences are the number of threads and cache type.
Older dual core processor doesn't enable thread for each core as compared to current generation such as i3, i5 and i7. Core i3 has the capability to run dual thread on each core, thus total threads number can run in core i3 is 4 threads. Same as goes to other processor in this family, i7 has up to 8 threads can be ran on (each 2 or 4 core).
Core i3 used new smart cache (L3 cache) instead of L2 cache, as defined by Intel:
"Smart Cache is Intel’s performance-maximized data storage, which allows each processor core to dynamically utilize up to 100% of available cache and obtain data from the cache at higher throughput rates"
For gamers, here is a benchmark i found.