How Does A Hard Drive Work?


Hard disk dissection

The average laptop in the shops for around $500 has somewhere in the region of 60GB of storage memory. You see that figure and think ‘wow ““ imagine all the movies, songs, images, files and documents I could save on that baby’, right?

But did you ever think about how it actually gets stored?

If you were to stack the equivalent capacity of CDs in front of you it would surely rise to eye-level. You can fit everything on those CDs onto that hard drive. Truly amazing for an invention that has its origins in the 1950′s and was first developed as a humble cassette tape.

 

How Does a Hard Drive Work – The Basics

hard-drive-parts

In order to fully understand a hard drive you have to know how one works physically. Basically, there are discs, one on top of the other spaced a few millimetres apart. These discs are called platters. Polished to a high mirror shine and incredibly smooth they can hold vast amounts of data.

Next we have the arm. This writes and reads data onto the disc. It stretches out over the platter and moves over it from centre to edge reading and writing data to the platter through its tiny heads which hover just over the platter. The arm, on the average domestic drives can oscillate around 50 times per second. On many high-spec machines and those used for complex calculations this figure can rise into the thousands.

Hard drives use magnetism to store information just like on old cassette tapes. For that reason, copper heads are used as they are easy to magnetise and demagnetise using electricity.

Storage and Operation

Hard-Drive-sections

When you save a file, the “˜write’ head on the arm writes the data onto the platter as it spins at high RPM often in the region of 4,000. However, it doesn’t just go anywhere as the computer must be able to locate the file later. It also must not interfere or indeed delete any other information already on the drive.

For this reason, platters are separated into different sectors and tracks. The tracks are the long circular divisions highlighted here in yellow. They are like “˜tracks’ on music records. Then we have the different sectors which are small sections of tracks. There are thousands of these from centre to edge of the platter. One is highlighted blue in the picture.

In Operation

When you open a file, program or really anything on your PC, the hard drive must find it. So let’s say that you open an image. The CPU will tell the hard drive what you’re looking for. The hard drive will spin extremely fast and it will find the image in a nano-second. It will then “˜read’ the image and send it to the CPU. The time it takes to do this is called the “˜read time’. Then the CPU takes over and sends the image on its way to your screen.

Let’s say you edited the image. Well now those changes must be saved. When you click “˜Save‘, all of that information is shot to the CPU which in turn sorts it (processes it) and sends it to the hard drive for storage. The hard drive will spin up and the arm will use its “˜write‘ heads to overwrite the previous image with the new one. Job done.

That is what that buzzing disc in your computer gets up to all day. Now, as I do with most of my articles here on MUO I shall leave you with a friendly word of advice:

If you want to look inside to further understand how does hard drive work, do so with an old one. There are a few reasons for this.

  • Once you pop open that drive, plugs on the screws will snap to tell the manufacturer you have been poking around in there. By doing this, your warranty is void immediately. Many drives actually have this warning printed on the side.
  • They’re expensive and carry a lot of important info so don’t just pop open the family PC to have a go at it. Pick up an old one on eBay.

tell us what YOU know about HDDs, share your thoughts 🙂

What Is A Processor Core?


Every computer has a processor, whether it’s a small efficiency processor or a large performance powerhouse, or else it wouldn’t be able to function. Of course, the processor, also called the CPU or Central Processing Unit, is an important part of a functioning system, but it isn’t the only one.

Today’s processors are almost all at least dual-core, meaning that the entire processor itself contains two separate cores with which it can process information. But what are processor cores, and what exactly do they do?

What Are Cores?


A processor core is a processing unit which reads in instructions to perform specific actions. Instructions are chained together so that, when run in real time, they make up your computer experience. Literally everything you do on your computer has to be processed by your processor. Whenever you open a folder, that requires your processor. When you type into a word document, that also requires your processor. Things like drawing the desktop environment, the windows, and game graphics are the job of your graphics card — which contains hundreds of processors to quickly work on data simultaneously — but to some extent they still require your processor as well.

How They Work


The designs of processors are extremely complex and vary widely between companies and even models. Their architectures — currently “Ivy Bridge” for Intel and “Piledriver” for AMD — are constantly being improved to pack in the most amount of performance in the least amount of space and energy consumption. But despite all the architectural differences, processors go through four main steps whenever they process instructions: fetch, decode, execute, and writeback.

Fetch

The fetch step is what you expect it to be. Here, the processor core retrieves instructions that are waiting for it, usually from some sort of memory. This could include RAM, but in modern processor cores, the instructions are usually already waiting for the core inside the processor cache. The processor has an area called the program counter which essentially acts as a bookmark, letting the processor know where the last instruction ended and the next one begins.

Decode

Once it has fetched the immediate instruction, it goes on to decode it. Instructions often involve multiple areas of the processor core — such as arithmetic — and the processor core needs to figure this out. Each part has something called an opcode which tells the processor core what should be done with the information that follows it. Once the processor core has figured this all out, the different areas of the core itself can get to work.

Execute


The execute step is where the processor knows what it needs to do, and actually goes ahead and does it. What exactly happens here varies greatly depending on which areas of the processor core are being used and what information is put in. As an example, the processor can do arithmetic inside the ALU, or Arithmetic Logic Unit. This unit can connect to different inputs and outputs to crunch numbers and get the desired result. The circuitry inside the ALU does all the magic, and it’s quite complex to explain, so I’ll leave that for your own research if you’re interested.

Writeback

The final step, called writeback, simple places the result of what’s been worked on back into memory. Where exactly the output goes depends on the needs of the running application, but it often stays in processor registers for quick access as the following instructions often use it. From there, it’ll get taken care of until parts of that output need to be processed once again, which can mean that it goes into the RAM.

It’s Just One Cycle

This entire process is called an instruction cycle. These instruction cycles happen ridiculously fast, especially now that we have powerful processors with high frequencies. Additionally, our entire CPU with its multiple cores does this on every core, so data can be crunched roughly as many times faster as your CPU has cores than if it were stuck with only one core of similar performance. CPUs also have optimized instruction sets hardwired into the circuitry which can speed up familiar instructions sent to them. A popular example is SSE.

Conclusion


Don’t forget that this is a very simple description of what processors to — in reality they are far more complex and do a lot more than we realize. The current trend is that processor manufacturers are trying to make their chips as efficient as possible, and that includes shrinking the transistors. Ivy Bridge‘s transistors are a mere 22nm, and there’s still a bit to go before researchers encounter a physical limit. Imagine all this processing occurring in such a small space. We’ll see how processors improve once we get that far.

Where do you think processors will go next? When do you expect to see quantum processors, especially in personal markets? Let us know in the comments below !

By Danny Stieben makeuseof.com

What Are The Differences Between Capacitive & Resistive Touchscreens?


It might not fully register, but we all know there are two types of touchscreens. There are those we find on expensive smartphones and tablets, which respond to the slightest touch, allow multi-touch and are generally highly responsive (unless you’re wearing gloves); and then there are those that have slightly longer response time, that require some pressure or a stylus, that don’t have multi-touch abilities but work no matter what you touch them with.

Whether you know what the difference is or not, you’ve probably experienced these differences yourself. When that happened, you might have wondered what causes them; why doesn’t your iPhone work when you’re wearing gloves? Why do touchscreens on feature phones behave differently from those of high-end smartphones? Why can’t you use just any old stylus on your iPad?

All these questions can be answered by two words: resistive and capacitive. The difference between these two touchscreen technologies answers all the above questions. Curious? Read on to find out exactly how it works. Note, however, that this is a simple explanation, and is not meant for engineers. Don’t expect to be able to build one of these by the end of the article!

Touchscreens In A Nutshell

difference between capacitive and resistive

Although touchscreens are becoming increasingly popular, they are by no means a new invention. The first touchscreen was invented back in the 1960s, and has gone through many changes and iterations to become the touchscreen we use today.

Touchscreens are not limited to smartphones and tablets, they are literally everywhere; from ATM machines, point-of-sale terminals, and navigation systems, to game consoles and even touchpads on laptops. Touchscreens are popping up everywhere, and are slowly taking over our lives, so the least we can do is know a bit more about how they work!

Resistive Touchscreens

The resistive touchscreen is the most common type of touchscreen. Except for modern smartphones, tablets and trackpads, most touchscreens we come in contact with are actually resistive touchscreens. As you’ve probably guessed, the resistive touchscreen relies on resistance. In that respect, it’s pretty intuitive to understand – the pressure you apply causes the screen to respond.

A resistive touchscreen is made out of two thin layers separated by a thin gap. These are not the only layers in the resistive touchscreen, but we’ll focus on them for simplicity. These two layers both have a coating on one side, with the coated sides facing each other inside the gap, just like two pieces of bread in a sandwich. When these two layers of coating touch each other, a voltage is passed, which is in turn processed as a touch in that location.

capacitive touchscreens

So when your finger, stylus, or any other instrument touches a resistive screen, it creates a slight pressure on the top layer, which is then transferred to the adjacent layer, thus starting the cascade of signals. Because of this, you can use anything you want on a resistive touchscreen to make the touch interface work; a gloved finger, a wooden rod, a fingernail – anything that creates enough pressure on the point of impact will activate the mechanism and the touch will be registered.

For this very same reason, resistive touchscreen require slight pressure in order to register the touch, and are not always as quick to respond as capacitive touchscreens such as the iPhone’s. In addition, the resistive touchscreen’s multiple layers cause the display to be less sharp, with lower contrast than we might see on capacitive screens. While most resistive screens don’t allow for multi-touch gestures such as pinch to zoom, they can register a touch by one finger when another finger is already touching a different location on the screen.

capacitive touchscreens

Resistive screens have been improving greatly over the years, and today many lower-end smartphones boast a resistive screen which is no less accurate than high-end devices. Some recent devices using resistive touchscreens are the Nokia N800, the Nokia N97, the HTC Tattoo and the Samsung Jet. Another well-known device using resistive technology is the Nintendo DS, which was the first popular game console to make use of it.

Capacitive Touchscreens

Surprisingly, it was actually the capacitive touchscreen that was invented first; the first one was built almost 10 years before the first resistive touchscreen. Nevertheless, today’s capacitive touchscreens are highly accurate and respond instantly when lightly touched by a human finger. So how does it work?

As opposed to the resistive touchscreen, which relies on the mechanical pressure made by the finger or stylus, the capacitive touchscreen makes use of the electrical properties of the human body. A capacitive screen is usually made of one insulating layer, such as glass, which is coated by a transparent conductive material on the inside. Since the human body is conductive, which means electricity can pass through it, the capacitive screen can use this conductivity as input. When you touch a capacitive touchscreen with your finger, you cause a change in the screen’s electrical field.

capacitive touchscreens

This change is registered, and the location of the touch is determined by a processor. This can be done by several different technologies , but they all rely on the electrical change caused by a light touch of a finger. This is the reason you cannot use a capacitive screen while wearing gloves – the gloves are not conductive, and the touch does not cause any change in the electrostatic field. Same goes for non-capacitive styluses.

difference between capacitive and resistive

Since capacitive screens are made of one main layer, which is constantly getting thinner as technology advances, these screens are not only more sensitive and accurate, the display itself can be much sharper, as seen on devices such as the iPhone 4S. And of course, capacitive touchscreens can also make use of multi-touch gestures, but only by using several fingers at the same time. If one finger is touching one part of the screen, it won’t be able to sense another touch accurately.

Which type of screen do you prefer? Do you like being able to use your touchscreen with any type of stylus or instrument, or do you value speed and accuracy over anything else? Share your opinions in the comments.

By Yaara Lancet makeuseof.com

What Is The Difference Between An LCD And An LED Backlit LCD Display?


This subject is complex because it’s simple. The differences between LED vs LCD TV are subtle, which can make it difficult to understand the difference. It’s an important distinction, however, because it can significantly impact image quality as well as price. I’m also going to explain the differences between LED displays – not all of them are built the same.

The Core Question – What’s LCD vs LED?

led vs lcd tv

LCD, or Liquid Crystal Display, is the fundamental display technology used by most monitors, televisions, tablets and smartphones. It consists of a panel of liquid crystal molecules that can be induced by electrical fields to take certain patterns which block light or allow it through.

Color LCD displays have green, blue and red sub-pixels in each pixel. The intensity of light allowed through each sub-pixel is carefully controlled to create a detailed picture capable of displaying millions of different colors.

However, the crystals create no light of their own. It’s possible to light an LCD using reflected ambient light (the Nintendo GameBoy Advanced operated in this way) but all LCD HDTVs have a backlight which shines light through the display.

In the past, HDTVs used cold cathode fluorescent lamps to provide this light. However, manufacturers noticed that using Light Emitting Diodes would provide equal light with less energy. It was also possible to turn individual diodes off when no light was needed, something that’s not possible with CCFL lighting.

Because the addition of LEDs for backlighting was the new feature, this was used to describe the new televisions. But the new LED TVs still use an LCD display, just like the previous models lit by CCFL tubes.

So, Why Is LED Better?

led vs lcd

CCFL tubes can’t be switched on or off while a display is turned on and can only be arranged in vertical or horizontal lines. This creates picture quality problems. Since the lighting is never turned off, dark scenes are hard to render properly, and the arrangement of the CCFL tubes can cause parts of a display to appear brighter than others.

LEDs, on the other hand, can be quickly switched on or off. This allows much better control of light. They also can be arranged in a grid across a display or in a ring around a display, which offers theoretically better light distribution. Finally, LEDs do not consume as much energy.

There are different types of LED displays, however, and each has different traits. I’ll explain each.

Edge-Lit LED

led vs lcd

The image above provides a basic example how an edge-lit display works. In this instance a green LED is shone inwards on a Christmas tree pattern. The light is guided along that pattern and creates a profile. In an edge-lit HDTV there are also light guides, but instead of trying to create a specific pattern they attempt to distribute light evenly across the interior of the television.

This technology can be used to create extremely thin displays, is generally low on power draw and relatively inexpensive compared to other LED variants. If you see an LED-backlit HDTV for a low price there’s a good chance it is edge-lit.

Edge-lit displays usually do not manage to be entirely even in their light distribution, so they suffer from uniformity issues (i.e. parts of the image appear brighter than others.) Some models offer local dimming. This feature precisely controls the light output of LEDs to display deeper black levels.

Full Array LED

led vs lcd tv

A full array LED display has a grid of LED lights behind the LCD display. They shine directly outwards, creating a bright and usually uniform picture. Most televisions with a full array are expensive, enthusiast models that offer local dimming. This can provide excellent black level performance.

There are, however, a few LED sets with a full array that lack local dimming. A television set up this way will provide the uniformity benefits of LED, but probably won’t offer black levels that are much, if any, deeper than a good display lit by traditional CCFLs.

RGB-LED

This rare technology uses colored LED lights to provide additional color and lighting control. This creates very precise colors and can also provide better detail in scenes with a lot of contrast. RGB-LED is technically a modifier of the other two types – there can be edge-lit and full array versions – but most displays with this type of backlight are full array.

There are not a lot of displays that use this technology. Dell is known to offer RGB-LED in its workstation laptops and there are some high-end televisions and monitors that offer this, such as Sony’s $5000 Bravia XBR8.

Displays with RGB-LED are almost always very, very good, but most people can’t justify the extra cost.

Conclusion

I hope this has clarified the difference between LCD and LED – or, rather, highlighted the fact that it’s not a difference so much as a confusion of terms.

If you’re wondering if LEDs are worth it over non-LED displays, the answer is that it depends. There are other competing technologies, like Plasma and OLED, which operate differently and have different traits.

Individual product quality is also a big deal. Some of the best displays in the world use LED backlighting – but there are also some very poor displays that use this technology, as well.

By Matt Smith makeuseof.com