Computer Architecture

 Let's examine the functionality and organization of the computer, and this is called the computer architecture. So a computer is a machine that transforms input data into output information through the execution of instructions of a software program. So therefore the components that find at any computer are the ones we see here in the picture. So we have input devices we have the CPU, we have storage, memory and output devices. So the input devices like the keyboard and the mouse are used to get data from the user or the environment and introduce it into the system. Then the CPU, the central processing unit executes the instructions of a program one by one fetches the data, does the operations and returns the results into the memory. And the main or primary memory, that you see here on the slides. stores all the data along with the instructions of the program that controls the computer. Then we have a set of output devices to send the obtained results back to the user, depending on their nature, so this is for example the screen, it can be the printer where can print something, or it can be the speaker if is audio results what we're looking at. The permanent storage devices that keep the program for future execution and data and information for future queries these are considered input and output devices since they perform both operations, because they have to input data and have the output data where they store it. So the architecture of modern computers is known as the Von Neumann architecture and its main features is that the main memory stores temporarily data and instructions. There's other architectures that were defined at the beginning of computing like for example the harvard architecture but they were more complex and  haven't been successful. So here on this slide we see how the Von Neumann architecture works you can see that all the components are connected to the system bus and this is formed by a data bus, the address bus, and a control bus. And data is just exchanged between components using the data bus. The address bus indicates which devices are being accesed and finally the control bus transport state signals between different devices. So this in short we have seen how the computer architect is formed and how functionality and organization of a computer is it.

Personal Computer Architecture

 We are going to see how the hardware in a personal computers is organized. So pc was designed with an open architecture and this means that it uses standard modular components and it's open. So we can add, replace, update it, swap them easily and the computer will identify and handle the new devices automatically. So the main component of a computer system is the motherboard or the main board. And this is a printed circuit board, it is called pcb, that holds the main components of the computer and all the electronics needed to communicate between them and and we can also use it to expand the system. So we could say that this is the central nervous system of the computer. The motherboard provides the electrical connections by which the other components of the system communicate. it's unlike a back plane since it also contains the central processing unit of the cpu and hosts other subsystems and devices. The form factor is the specification of the motherboard or main board and specifies the dimensions, the power supply type, locations of mounting holes, number of ports on the back panel, etc. So in IBM PC compatible industry, standard form factors ensure that parts are interchangeable across competing pc vendors and generations of technologies. And this in contrast to enterprise computing were form factors ensure that server modules fit into existing rack mounting systems. So traditionally the most significant specifications is for that of the motherboard and it generally dictates the overall size of the case. So the most used form factor for IBM pc compatible motherboard is atx, that's stands for advanced technology extended and its derivatives. Small form-factor main board mini-ITX is the de facto standard and here on the slides we see a couple of them and you can see more or less what size they have comparing them to the pen you can also see here on the slide. A power supply unit PSU is responsible to convert AC to low-voltage required regulated dc power and this is needed for the internal components of the computer. Modern personal computers universally use switched-mode power supply and some power supplies have a manual selector for input voltage, while others automatically can adapt to the supply voltage that is needed. Most modern desktop personal computer power supplies conform to the atx specifications, which includes form factor and voltage tolerance. So atx power supply unit supplies +3.3V, +5v, +12v and -12v. While an atx power supplies is connected to the mains supply it always provides a +5v standby which is 5VSB voltage so that it can standby functions on the computer and certain peripherals are powered. ATX power supplies are turned on and off by and originated signal from the motherboard. A computer case which is also known as the computer chasis or the computer tower, the system unit, the cabinet, the base unit there's lots of words that are used to to give a name to the computer case. This is the enclosure that contains all the components of the computer. It's sometimes also referred as the CPU which is incorrect because it contains the CPU on the motherboard, but it contains a lot more. So cases come in many different sizes, there are all these form factors and they determine the size and shape of a computer case. So form factors for rack-mounted and blade servers may include precise external dimensions as well, since these cases make themselves fit into specific enclosures. So a case designed for an atx motherboard that we've seen in the previous slide and the power supply may take on several forms that you might have seen you have, for example the vertical tower, which is designed to sit on the floor, it's vertical and the heigth is bigger than the width, we also have flat desktop ones which are flat and then obviously the height is less than the width. And we also have them like in a pizza box form in which height is less than five centimeters and this is designed to sit on the desk under computer's monitor, so you can put the monitor on top of it. Tower cases are often categorized as mid-tower, mini-tower or full tower. And full tower case are typically larger in volume than desktop cases so they have more room for drive bays and expansion slots. Desktop cases and mini-tower cases are popular in bussines environments where space is at a premium. So for high performance computers heat dissipation is a major issue that has to be taken into account. And these computers have their own form factor and case design. So, a disk bay is the place reserved for storage devices such as hard disks, cds, dvd units and these are all called bays. And the number we have depends of the size of the case, depends on the the amount that fit into it. So we've see a few internal components of a personal computer and we are going to see how they interface with external devices. So the computer as a number of connectors available to connect external devices that we've seen in previous videos and these connectors are called ports and in a standard computer well there's lots of ports that you can use to connect different external devices. Like for example screen ports, like VGA, DVI, HDMI to connect screens and another video devices, Sound ports that you can use to connect headphones, speakers, microphones for audio. General-purpose ports like USB that you can use to connect lots of things, hard disks, printers, scanners, the mouse the keyboard, all the other devices we've seen in previous videos. And there are network ports like Gigabit ethernet network interface adaptors, or bays that you can use for different type of flash memory card for example. In older computers you can also find serial ports or parallel port for printers or dedicated mouse and keyboard ports and moded ports for example. And other ports, like for example firewire buses. But nowadays we don't find these dedicated ports so much anymore because USB is the standard technology to connect any kind of devices to your personal computers. For USB there are several versions. The currrent one is three point one which supports very high transmission capacity wich is also called bandwidth. And the old USB 1.0 port that is now not suitable anymore for high bandwidth devices such as hard disks. USB 2.0 is still being used and, this or higher version ports should be used to connect them. Thunderbolt is another high-speed general-purpose port that can be found mostly in apple computers. So we've looked a little bit in this video on the computer hardware and how it's organized in your personal computer.

UPValenciaX: ISC101.2x Information Systems and Computer Applications, Part 2: Hardware