What is a Processor Or CPU?

What is a Processor Or CPU?

The CPU (Central Processing Unit) or processor is the brain of the computer – it’s where all the calculations are carried out. Short of gaming, pretty much all the work a computer does is carried out by the CPU; whileRAM and hard drives are important, they simply act as storage while data manipulation is carried out by the processor.

The die or internals of Intel’s i7 980x – the most powerful consumer CPU currently

… and the same processor held in the hand for a size reference

Clock Speed

One of the most common things you’ll see when looking at CPU specifications is the processor’s clock speed, measured in gigahertz (GHz), with 1GHz being equal to 1 billion hertz or cycles per second. This means that a 1GHz processor is able to carry out 1 billion calculations every second. As a general rule of thumb a processor with a higher clock speed is more powerful than one with a lower clock speed.

However this isn’t the whole story, as different CPUs can do different amounts of work per cycle. One way to understand this is to imagine two people trying to fill identical swimming pools from a well with nothing but buckets. If both buckets were the same size, the faster person would be the one who can make more trips between the well and their swimming pool in the same time frame. However, the slower person could fill their pool just as fast if they carry more water per trip with a bigger bucket. 

Multiple Cores

When looking to buy a new computer, you’ll be constantly barraged with mentions of cores – dual cores! Quad cores!

Hexa-core processors! What does it actually mean?

Up until 2004, all processors had just one core, or processing unit. A processor was made faster by increasing that core’s clock speed. The disadvantage to this was that higher clock speeds generated much more heat, leading to massive, noisy heatsinks. It eventually reached the stage where it was simply infeasible to keep increasing the clock speed.

The solution was to create a processor with two cores – that is, a single processor with two smaller, lower speed processing units which can carry out different instructions. The benefit in this is obvious – why force a single unit harder and harder to do lots of things at once when you can split the work between two slightly less capable units? Many hands make light work, as they say.

The first generations of dual core processors – the Intel Celeron D and AMD Athlon 64 X2 families, for example – weren’t much more efficient than their single-cored predecessors. In fact, before the technology was perfected they generated more heat than ever. However, over time they’ve become better and better; most new computers have at least two cores, with single core CPUs used only for the absolutely cheapest computers (as well as for applications where lots of processing power simply isn’t needed, ie netbooks).

Most of the performance gains do come down purely to clock speeds again. As an example, let’s compare a 3.0GHz dual core processor with a 2.6GHz quad core processor. This means that the dual core processor has 2 cores each running at 3.0GHz, giving the “equivalent” of a single core processor running at 6.0GHz. Although each core on the quad core processor is running 400MHz slower, there are four cores – 4 cores each running at 2.6GHz gives the “equivalent” of 10.4GHz.

So by that logic, surely all quad core processors must be better than dual core processors, and all hexa-core processors must be better than quads, right? Well, it’s not quite as simple as that, because it depends on what you want to do with the computer. Most of the time computers are now used to doing lots of different things at once; opening a lot of tabs in a web browser, word processing, listening to music and instant messaging all at the same time. This is where multi-core processors excel, as they are able to split up the tasks and distribute them between the cores; the more cores you have, the more your CPU can handle at once.

However, there are some single tasks which require lots of processing power – editing video, working with large images in Photoshop or playing games, for example. Up until very recently most computer applications haven’t been designed to make proper use of multiple cores. In this case, a processor with fewer cores at higher clock speeds will perform better. 

Cache

When doing some deeper research on different CPUs, you may come across cache, measured in kilobytes (KB) or megabytes (MB). This is a place where the most frequently used data is stored so that it is quickly accessible by the processor. Most recent CPUs have at least 2 levels of cache (L1 and L2), with newer and more powerful ones having a third level (L3). L1 is the fastest but smallest level of cache, whereas the higher levels tend to have much higher quantities but are slower (although still faster than accessing the data from theRAM). Most processors split the cache up amongst the cores, although some do have a single cache for all cores to access. In almost all circumstances more cache is better.

AMD vs. Intel

Although there used to be many companies that used to mass market CPUs, the vast majority of the desktop and laptop CPU market share is split between two companies; AMD and Intel. While other companies such as ARM and VIA are still around and producing processors for other sectors (mobile devices and low power commercial uses, respectively), they do not produce processors for desktops and laptops.

So, what’s the main difference between AMD and Intel processors? It used to be efficiency – AMD processors would be just as powerful as Intel’s while performing at lower clock speeds. Intel focused on increasing clock speeds whereas AMD focused on increasing the amount of work done per cycle.

Right now the main difference is value and backwards compatibility vs. performance. At most performance levels AMD tends to produce processors at a more competitive rate to Intel. Furthermore, AMDs new CPUs (using the AM3 socket) are still compatible with older AMD-based motherboards with the AM2+ socket, making it relatively painless to upgrade to the latest processor technology.

Intel’s instead decided to make a clean break with its new processors, introducing two new sockets (Socket 1156 and Socket 1366) and making backwards compatibility impossible. However, Intel’s most powerful processor is 25-50% faster than AMD’s - the only downside is that it costs over three times as much!

To put it another way, for those looking to upgrade from an older AMD-based system, those looking for a good balance between price and performance and those who don’t mind going without cutting edge technology, an AMD-based computer makes the most sense.

On the other hand, for those where money is no object or performance is particularly important, an Intel-based system is probably a better bet.

Of course, this is all assuming you’re looking into building your own computer. If you just go to a store your mind will be made up for you; 80% of the time the computer will be built around an Intel CPU. That’s by no means a bad thing; you don’t need to go hunting for an AMD computer necessarily. Just bear this in mind if you look into building your own computer.

CPU Heatsinks

With all the work that the CPU does in such a small space it’s not surprising that they tend to generate a lot of heat. Of course, this heat has to go somewhere – if the CPU gets too hot it’ll be damaged and won’t work anymore. There are a lot of delicate electronics in there!

That’s where the CPU heatsink comes in. Just look for a big hunk of metal with a big fan on it. That’ll be the heatsink! The CPU is under that, and it’s the only thing keeping your CPU from melting itself to your motherboard. Just kidding! If for some reason the CPU doesn’t get cooled properly it’ll shut itself off before any real damage can be caused.

So how does a heatsink work? Well, the heatsink uses levers or screws to keep the heatsink pressed tightly against the CPU. A tiny amount of thermal paste between the two removes absolutely all the gaps. Heat is then transferred from the surface of the CPU’s heat spreader to the heatsink via conduction. The heat spreads throughout the heatsink out to the edges of the heatsink, which are split into lots of thin fins. This greatly increases the surface area of the heatsink so when the fan on top blows down it pushes cooler air over the hot fins, taking heat away from the heatsink.

The only problem is that the stock cooler doesn’t do the best job in the world. Yes, it keeps the processor cool enough that it doesn’t overheat, but it usually doesn’t do it efficiently or quietly. As a result the CPU heatsink is often the noisiest part of the computer.

There are many manufacturers who realise this is the case, so you’ll find lots of companies which sell after-market CPU coolers. These tend to be much bigger, providing many more fins and a much, much larger surface area for the heat to be transferred away from the heatsink. A bigger heatsink also means that it can carry a larger fan which can spin slower to move the same amount of air, thus creating next noise. 

To move the heat faster after-market coolers tend to use more heat pipes, which use liquids to transfer heat faster to the far ends of the heatsink. You can see that the heatsink before, the Scythe Mugen 2, has 5 heat pipes which go from the top of the heatsink, all the way down and through the main block before moving back up the other side. Compare that to the size of the stock AMD heatsink, and you can see why it can keep a processor at room temperature while staying pretty much silent!