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A Buying Guide for newbies – why 'clock speed' isn’t everything

This guide is to help people better understand what's what in a CPU (Processor) so they can make an informed choice when choosing one to buy for a new PC or upgrading an old one, a lot of people simply go off the actual clock speed of the CPU but that's just part of its performance influence. There are many other factors to consider when trying to 'gauge' the performance of a processor compared to others

The main parts of a processor are (with examples):-

CLOCK SPEED (3Ghz – 3 Gigahertz)
This is the overall clock cycle speed of the CPU, the code in the CPU is executed at these many cycles-per-second, the faster the clock speed → the faster the CPU works at.

(2 cores / 4 threads)
A Processor that has multiple cores (for example 2 cores) is almost the same as having 2 processors, it means the processor has multiple execution cores and can do twice (or more) as much work thus making it twice (or more) as fast. Each core processes 1 'Thread' of data at a time, on some processors a feature called 'Hyper-Threading' is available, this is where each 'core' can execute 2 threads of data at the same time, e.g. if core 1 is only running at 50% executing the instructions on its 1st thread then it can use the other 50% to execute code on its second thread, these are sometimes referred to as 'Logical Cores' (Virtual Cores)and actual cores referred to as 'Physical Cores' – a Logical Core is not as good as having a dedicated Physical Core... that is too say a Quad-Core (4 Cores executing 4 Threads) processor is superior to a Dual-Core processor with Hyper-Threading (2 Cores executing 4 Threads).

CACHE (L1, L2 & L3 Cache)
This is the on-board memory inside the processor, the more memory it has, the more data it can store, thus the less 'fetching' it has to do to-and-from the main computer memory (RAM) and thus increasing efficiency and speed. The cache usually has 2-3 'Level's of memory, the more memory it has the better.

Simply put these are the 'bus' speed ratings, when used in conjuction with supporting motherboard it refers to the speed data can be transferred between the processor and north/south bridge, basically the speed at which the data travels across the motherboard to other components such as Hard-Drive, Memory or Graphics card.

In short term, this is the size of the manufacturing process used in the processor (for e.g. 65nm, 45nm or 32nm), the smaller the number, the more transistors can be placed in the CPU and thus more data processed per clock cycle and therefore more speed,  it is also usual to see better energy efficiency and less heat generation.

MICRO-ARCHITECTURE (Sandy-Bridge, Ivy-Bridge)
This is the actual design of the chip, each new architecture usually brings new chip design and new and/or improved functions, one example would be Ivy-bridge has Tri-Gate Transistor Technology, this obviously can have a big role in improved performance over chips with older Micro-Architecture.

(75 watt)
This part refers to the max power consumption by the chip, this helps buyers understand if their current setup's power supply is enough or if they need to upgrade that too.

The stepping Level is a 'Version' number for that model of chip, sometimes the same model of chip me have some small changes made to fix problems or make slight improvements, one should always check the background of a chip thoroughly to make sure your not buying an older version that may not perform as well.

Now you can see that simply going off the 'clock speed' is not the important factor, you can have two CPU's with same clock speed, same internal cache memory and even the same amount of cores/threads – but one may massively out-perform the other, for example one could be made from a 65nm process and the other a 32nm process meaning already it may have somewhere in the region of twice as many transistors (meaning it could do around twice the workload), it may also have a new architecture that brings massive performance boosts. You can even get Identical chips with every single major component the same except 'Stepping Level' which means very small change has been made to improve something, an example of this would be the Core2Quad Q6600 (B3 stepping) which had a later version (G0 stepping) which lowered heat emission and allowed for better over-clocking.

I hope you find this guide useful next time your planning on buying a new processor.
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