If you want a plain and simple answer, then generally speaking, within the same generation Core i7s are better than Core i5s, which are in turn better than Core i3s. Nope, Core i7 does not have seven cores nor does Core i3 have three cores. The numbers are simply indicative of their relative processing powers.
Their relative levels of processing power are also signified by their Intel Processor Star Ratings, which are based on a collection of criteria involving their number of cores, clock speed (in GHz), size of cache, as well as some new Intel technologies like Turbo Boost and Hyper-Threading
Core i3s are rated with three stars, i5s have four stars, and i7s have five. If you’re wondering why the ratings start with three, well they actually don’t. The entry-level Intel CPUs — Celeron and Pentium — get one and two stars respectively.
Number of cores
The more cores there are, the more tasks (known as threads) can be served at the same time. The lowest number of cores can be found in Core i3 CPUs, i.e., which have only two cores. Currently, all Core i3s are dual-core processors.
Currently all Core i5 processors, except for the i5-661, are quad cores in Australia. The Core i5-661 is only a dual-core processor with a clockspeed of 3.33 GHz. Remember that all Core i3s are also dual cores. Furthermore, the i3-560 is also 3.33GHz, yet a lot cheaper. Sounds like it might be a better buy than the i5. What gives?
Even if the i5-661 normally runs at the same clockspeed as Core i3-560, and even if they all have the same number of cores, the i5-661 benefits from a technology known as Turbo Boost.
Some Important Terms to understand to get better at i3, i5, and i7.
Intel Turbo Boost
The Intel Turbo Boost Technology allows a processor to dynamically increase its clockspeed whenever the need arises. The maximum amount that Turbo Boost can raise clockspeed at any given time is dependent on the number of active cores, the estimated current consumption, the estimated power consumption, and the processor temperature.
For the Core i5-661, its maximum allowable processor frequency is 3.6 GHz. Because none of the Core i3 CPUs have Turbo Boost, the i5-661 can outrun them when it needs to. Because all Core i5 processors are equipped with the latest version of this technology — Turbo Boost 2.0 — all of them can outrun any Core i3
Cache size
Whenever the CPU finds that it keeps on using the same data over and over, it stores that data in its cache. Cache is just like RAM, only faster — because it’s built into the CPU itself. Both RAM and cache serve as holding areas for frequently used data. Without them, the CPU would have to keep on reading from the hard disk drive, which would take a lot more time.
Basically, RAM minimizes interaction with the hard disk, while cache minimizes interaction with the RAM. Obviously, with a larger cache, more data can be accessed quickly. All Core i3 processors have 3MB of cache. All Core i5s, except again for the 661 (only 4MB), have 6MB of cache. Finally, all Core i7 CPUs have 8MB of cache. This is clearly one reason why an i7 outperforms an i5 — and why an i5 outperforms an i3.
Hyper-Threading
Strictly speaking, only one thread can be served by one core at a time. So if a CPU is a dual core, then supposedly only two threads can be served simultaneously. However, Intel has introduced a technology called Hyper-Threading. This enables a single core to serve multiple threads.
For instance, a Core i3, which is only a dual core, can actually serve two threads per core. In other words, a total of four threads can run simultaneously. Thus, even if Core i5 processors are quad cores, since they don’t support Hyper-Threading (again, except the i5-661) the number of threads they can serve at the same time is just about equal to those of their Core i3 counterparts.
This is one of the many reasons why Core i7 processors are the creme de la creme. Not only are they quad cores, they also support Hyper-Threading. Thus, a total of eight threads can run on them at the same time. Combine that with 8MB of cache and Intel Turbo Boost Technology, which all of them have, and you’ll see what sets the Core i7 apart from its siblings.
Some Specifications for reference purposes
| Description/ Used in | Cores / HThreads/ Cache | Turbo Boost | CoreCode / Year | Trigate/ Size / RAM Speed | Socket | Avg Price | |
|---|---|---|---|---|---|---|---|
| Core i7 | Top End Science & Games | 4 / 4 8MB | Yes | Ivybridge 2012 | Yes 22nm DDR3 1600 | 1156 | Rs 20000 |
| Core i5 | Mass Market Business & Games | 2 / 4 6MB | Yes | Ivybridge 2012 | Yes 22nm DDR3 1600 | 1156 | Rs 13500 |
| Core i3 | Entry Level Modern Home PC's | 2 / 2 3MB | No | Ivybridge 2012 | Yes 22nm DDR3 1600 | 1156 | Rs 10000 |
| Pentium | Last Years Technology Very Entry Level PC's | 2 / 0 2MB | No | SandyBridge 2011 | No 32nm DDR3 1066 | 1155 | Rs 5000 |
| Celeron | Slow Last Years Tech Appliances | 2 / 0 2MB | No | SandyBridge 2011 | No 32nm DDR3 1066 | 1155 | Rs 3500 |
| Atom | Ultra Low Power Netbooks & Appliances | 2 / 2 1MB | No | CedarTrail 2012 | No 32nm DDR3 1066 | 559 | Rs 2000 |
Hope so it'll help you finding out which laptop you should buy...
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