For starters, the Pentium only has 3MB of L3 cache memory while the i3 has 4MB. More cache directly translates to lesser main memory accesses, which is much slower compared to cache memory. Controllers on the Pentium are also slower compared to those found on the i3. The memory controller of the i3 supports 1066Mhz and 1333Mhz modules while the Pentium would supports 1066Mhz and would automatically scale down the 1333Mhz module you put in. This is also the case when it comes to the graphics controller of the both processors. Whereas the i3 graphics controller runs at 733Mhz, that of the Pentium is only able to run at 533Mhz
Also on the integrated graphics aspect, the Pentium lacks support for the Intel Clear Video HD Technology. This technology covers the playback of video and includes such features as dual video decode for Blu-ray, deep color and extended gamut, and other high-end options for video playback. All this can be found on the i3.
Lastly, hyper-threading is disabled in the Pentium but not in the i3. Hyper-threading allows the operating system to see each core as two virtual cores. While the Pentium is seen by the operating system as having two cores, the i3 is seen as having four due to hyper-threading. Hyper-threading is known to provide performance improvements in applications that are optimized for multi-threading, where the tasks are broken up and pieces are assigned to different cores.
1. The Pentium is a low-end version of the Core i3
2. The Pentium has less cache than the i3
3. The Pentium memory controller runs slower than the i3
4. The graphics controller on the Pentium runs slower than on the i3
5. Intel Clear Video HD Technology is present on the i3 but not on the Pentium
6. The Pentium lacks hyper-threading found on the Core i3
ummm the OP asked about the PENTIUM 4 (IV) not the PENTIUM DUAL CORE - totally different all together
Pentium 3 yet again different all together but in ways is more related to a modern system then a pentium 4 (pentium pro -> pentium 2 -> pentium 3 -> pentium m -> core duo -> core 2 duo -> core i7 - etc)
Pentium 4 and Pentium D = NETBURST architecture (low ipc, high clock speeds intended for marketing to make them sound good) - not in any way related to PENTIUM DUAL CORE (Core2/Conroe aswell as Core ix/nehalem architecture variants)
In todays market the Pentium Dual Core's are considered a budget processor, one up from a celeron pretty much and have basic features but overall arent too bad for normal every day tasks.
Just remember there are different series and architectures with similar names.