I shall explain. Sorry I'm late!
Alright, what midi_sec pointed out is important. That single thread rating? Worse then a 5-6 year old Pentium D 950. And most modern i3s are actually really powerful. Many gamers use i3s in their builds due to their sheer single thread performance(which Minecraft loves!). Also, besides the registries, another reason why you are enjoying decent performance is the 4 cores of your processor. Each core allows the system to split work between them. It's why AMD FX series processors can beat high end Intel cpus in some benchmarks, their sheer amount of cores(FX-8350 has 8, FX-6300 has 6). But minecraft can't use more then one thread(not including small side code and Java garbage collection.) I'll give you an example of how it'll perform. My pentium d 950(Now replaced with an athlon x4 860k) got about 15-20 FPS in a mid-game base in TPPI. It has double the single thread rating of that thing's processor. And that's with a dedicated graphics card taking work off the CPU. :/