Pentium vs Intel core i3



3 major differences:

- Pentiums have slightly slower clock speed vs. Core i3 models.
- While both have two physical cores, the Core i3 also has hyper-threading which can increase performance by ~ 20%.
- Core i3 models have Quick Sync technology for quickly encoding/decoding HD video.

 
Both pentium and intel core 3 are pretty much the same, but there are few significant things that is different.
Pentium has 3MB of L3 cache memory while the i3 has 4MB.
Pentium lacks support for the Intel Clear Video HD Technology
Pentium does not have hyper-threading while the i3 has.