More on 'the mother of all boards'
Last week I men- tioned that the
motherboard is a sandwich of printed circuits that act like roads and highways that you find in a city, connecting places and providing a medium of transport between them. These 'roads' are known as "system buses" because they carry electronic data in binary form that in turn are represented by different voltages in the circuits. Strictly as a comparison, these highways also have means of regulating traffic-devices that act like traffic lights for example even though their workings are more complex and dynamic than those of actual traffic lights. I also mentioned that the motherboard provides the infrastructure for the various components of the machine to function effectively. So understanding how the motherboard works is crucial if you want to get a good understanding about how the computer works in general.

System buses

While providing services such as supporting basic input and output functions, the system buses play a critical role in the performance of your computer. I also have to mention here that the defining component of a motherboard is its chipset - two prominent processor chips on the motherboard that are termed as the 'north bridge' and the 'south bridge'. There are many other components that form the motherboard but this week we will focus our discussion on system buses.

The components inside your computer talk to each other in various different ways. Most of the internal system components, including the processor, cache, memory, expansion cards and storage devices, talk to each other over one or more "buses".

A bus, in computer terms, is simply a channel over which information flows between two or more devices (technically, a bus with only two devices on it is considered by some a "port" instead of a bus). A bus normally has access points or places into which a device can tap to become part of the bus, and devices on the bus can send and receive information from other devices. The system buses can be divided physically as internal buses (those printed onto the motherboard for communication among internal devices) and external buses (interfaces to secondary devices which are not part of the motherboard). All these data buses can also be categorised as 'serial' or 'parallel' buses as well, but we will come to that later.

You may remember our discussion about processors, where we discussed the three main components of the processor as the Arithmetic/Logic Unit (ALU), Control Unit (CU) and Memory. As a matter of fact, even though the processor itself contains a little bit of its memory within it (this is known as 'Level 1 Cache Memory' and since it is inside the processor itself, it is very fast, but...), most of the computer's memory is outside the processor and plugged into the motherboard - yes I am referring to Random Access Memory (RAM). There are many types of RAM and sometimes these different types function differently (more on this later). So since these memory units are outside the processor, it is the motherboard that provides the data link between the processor and RAM and this is known as the "Front Side Bus" (FSB) - one of the more important buses on the motherboard.

As you already know, modern processors can process enormous amounts of data at super-fast speeds, but it is a very difficult task to make the computer memory act as fast as the processor and transport data at such high rates. In other words, the processor could be capable of processing more data than what the memory can provide in a given time which could result in the processor being idle most of the time with nothing to do while it waits for more data to come in and as a result a lot of processor time being wasted. This would look a lot like a typical traffic jam on a busy street.

So to solve this problem, we have to make the memory run faster and enable fast data rates between the memory and the CPU. This is where the FSB comes in to provide faster data rates between the memory and the CPU by increasing the speed and capacity of data flow. Take a highway for example and think of how we can enable more traffic to flow in a given period of time. Now consider the two types of data buses - 'serial' and 'parallel'. One way would be to increase the number of lanes in the highway so that more vehicles could move through and this is essentially what parallel system buses attempt to do. When it comes to electronic data, we can provide parallel wires and thus increase the data flow. The other way to increase the flow of traffic is to make the vehicles move faster and faster. This means to increase the speed at which data flows through the wires and one way of doing this is by increasing the frequency of the data bus and theoretically this method can be applied to both serial and parallel busses. You may wonder then as to "why not have parallel busses that functions at high frequency?" In practice however, this is not possible due to issues such as 'interference' and 'noise' in the medium which I will explain when we talk about networks.

Even though 'increasing the number of lanes' was a popular option of increasing the data rates in the past, recent experiments and research in data communication technologies suggest that the way to progress is through serial buses for increased data rates. As a result, serial buses such as USB (Universal Serial Bus) and 'Firewire' have become very popular as they provide fast data rates.

There is a lot more to be learnt about the motherboard as this discussion continues (in fact we haven't discussed the most important parts yet). Until then, write in with your ideas and questions to technopage.

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