Introduction
The difference between Core i3, Core i5 and Core i7 can be explained by their relative processing power, which means that Core i7 is better than i5 and i5 is better than i3. However, strictly speaking, the main differences between the three cores can be analyzed based on the number of cores, cache size and Hyper-Threading capability of the processors.

The number of Cores
The number of cores reflects the number of tasks that can be performed simultaneously by a CPU. The i3 processors have only two cores, while most of the i5 and i7 processors are quad cores. Therefore, based on the number of core, both i5 and i7 have a higher processing power compared to Core i3 processors.

Cache size
If a CPU finds it is using the same data over and over, it stores the same data in its cache, which is similar to RAM. According to Parkinson, both cache and RAM are used for holding frequently used data and without them a CPU would be forced to keep on reading from the hard disk, which is a time consuming task. RAM reduces interaction with the hard disk, while the cache reduces interaction with RAM. If a CPU has a large cache, it means more data can be processed quickly. According to Parkinson, all Core i3 processors have 3MB of cache; i5 processors have 6MB of cache while i7 processors have 8MB of cache, which explains why i7 performs better than i5 and i5 outperforms i3.

Hyper-Threading
According to Parkinson, D., only a single thread can be served with one core at any given time. Therefore, if a CPU is a dual core, it follows that only two threads can be served at the same time. However, with the introduction of Hyper-Threading technology by Intel, it is now possible to serve several threads at the same time. For example, the dual core i3 can serve two threads per core, which means that four threads can run at the same time. Although 15 processors are quad cores because they do not support Hyper-Threading, they can serve the same number of threads as the i3 processors. However, i7 are the crème de la crème because they are both quad cores and can support Hyper-Threading. Therefore, if a user is using a PC to do multiple tasks simultaneously it would be advisable to go for i5 or i7. In case a user uses a PC to perform tasks such as reading news or downloading a bit of music, then a cheaper i3 processors would be advisable.

Conclusion
This discussion has provided an explanation on the differences between the three cores: i3, i5 and i7. As shown in the discussion, the processing power of each core is based on the number of cores, cache size and Hyper-Threading capabilities. Based on these attributes, i7 is better than i5, and i5 performs better than i3.