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HARD DRIVE

Your Hard Disk or sometimes called a Hard Drive, is the main storage space inside your PC. Itis a permanent storage component unlike the RAM (system memory). It is possible for yourcomputer to function without a hard disk, however it would be basically useless to you as youwould not be able to use an Operating system or have any programs to use.

Hard disks use a circular hard platters to store data on. They are in pristine condition with amirror like finish to them. These platters are locked away inside a steel casing as unclean aircan easily ruin a hard disk. This is why you should never remove the casing from the hard disk,it is very unlikely you will be able to put it back together as a working component.

Above you can see a labelled diagram of a hard disk. The model is a SCSI (Small ComputerScientific Interface) You can see the hard platters on top of each other with a set of arms whichhold the read/write head. The speed of the arm is truly amazing as well as the accuracy of thehead which can read and write to perfection on a platter which is rotating around 7200Rpm. Thehard disk looks a very simple idea and probably is, however a lot goes on before the simple

writing to the disk its self. We will explain a little more later in the article.

How does the hard disk store data?

On each of the platters there is a thin layer of magnetic film. Data storage on hard disks is verysimilar to that of a cassette tape. Data is stored in many 1's and 0's. These binary digits arearranged in different ways to represent different characters. When these are read back by thehead the data is retrieved and processed.

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File Systems

A file system is the way in which your computer stores data on the hard disk. The most commonfile systems are FAT16 for older computers, FAT32 and NTFS. FAT stands forFile AllocationTable. NTFS stands forNT File System. Both have advantages and disadvantages. FAT16 wasa very limited file system in the way that it would store data very in-efficiently, every file would

take up a minimum of 32Kb in space as this was the minimum cluster size in a FAT16 system.Also it was only capable of using hard disks upto 2Gb in size. FAT32 solved this problem byreducing the cluster size to 4kb which saved a lot of wasted space and also allowed disk sizesup to 2 Terra bytes. NTFS is believed to be a far greater file systems than any of the FAT's. Thecluster sizes can be altered to anything as low as 512bytes which means almost no wastedspace on the hard disk. The maximum disk size is a unbelievable 18.5 x 10 bytes, which isvery big !!!. NTFS also has added security for file loss.

Measuring the Speed of a Hard Disk

There are various ways of measuring the speed of the hard disk. The main ones are themaximum data transfer rate, the spindle rotation speed and the seek time.

Maximum Transfer Rate - This is the highest amount of data that can be transferred persecond. Common forms of hard disks come with an ATA format. the speed rating of an ATA100disk would be 100Mb/s. Likewise a ATA66 disk would be able to transfer a maximum of 66Mb/s.

Spindle Rotation Speed -The rotation speed of the disk really is the basis of the other twofactors of hard disk speed. The faster the rotation speed, the more data can be written persecond and the quicker it is to find the correct data on the platter.

Seek Time -The seek time of a hard disk is the average time it takes for the disk to find thedata you need on the platters. A fast spinning, highly accurate and responsive disk will have ashorter seek time and will perform much better, especially when the data is scattered around thedisk.

Disk Fragmentation

All versions of Windows come with a disk defragmenter. But what exactly is fragmentation? Asyou use your computer daily files get written and deleted constantly from the disk, either byyourself or by the operating system creating and removing temporary files. This process leavethe disk in no sort of order and when new file are written to the disk they start to get written inthe gaps on the disk. The fact that single f iles are written in different parts of the disk means thatthe disk has to go round the disk reading different parts instead of just streaming the datastraight off the disk. This is called Fragmentation. The defrag program within windows sorts outthe files into order again to make the disk perform faster.

Connection Types

There are currently 3 connections for a hard disk. IDE (or ATA) SCSI and Serial ATA. The mostcommon is the IDE interface. This provides an 80 pin connection to most standardmotherboards and you can't normally go wrong buying an IDE drive for your machine. SCSIconnections often require extra hardware unless its built into your motherboard. SCSI hard disksare often faster but more expensive than there IDE counterparts. The final type is the newesttype. Serial ATA does away with parallel data transfer which has its problem of large wires andelectrical interference. The Serial ATA standard is more reliable and uses smaller un-obtrusivewires. Smaller wires also means better air flow for your case.

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GRAPHIC CARD

The graphics card is responsible for delivering the image you see on your PC monitor. Its GPU(Graphics Processing Unit) processes the machine code and changes it into a signal to themonitor. There are many factors to a graphics card. Choosing one can be a tricky businessthese days as there is so much technology that is different in each new graphics card release.More of these later in the article

Graphics Acceleration

When PC first came and for some time after, the graphics cards purpose was only to display theimage on the screen. The amount of memory you got on a graphics card was very small andwas not needed to a great extent. Today's graphics cards do more than just display an image,they help the processor with the job of processing when it comes to the graphics. The graphicscard would in effect accelerate the process of displaying the image on screen.

This was needed when the 3Dgaming world took the centre stage.

The speed required to process theimages on screen at 60 frames persecond and process the code for thegame itself was simply too much fora CPU to handle on its own and sothe games would simply crawl alongat a very slow pace. The graphicscard would use some of its own builtin instruction logic to added thingssuch as textures lighting effects, fogeffect and bump mapping to give a

far more detailed picture. Also the speeds of graphics cards have improved a great deal in orderto let these effects be used without the problem of the frame rate dropping.

AGP or PCI Express

Two types of Graphics card available today are the AGP and PCI-e versions. The AGP(Accelerated Graphics Port) is the older of the two technologies but still quite popular as manypeople still have these slots incorporated into there motherboards. The PCI-Express (PeripheralComponent Interconnect) version has been around for a couple of years now and new graphicscards and motherboards alike are using this technology. PCI express offers a greater scope fordata transfer to and from the graphics card and main memory.

How do you measure the speed of a graphics card?

Measuring the speed of the graphics card is a lot more difficult than with the CPU or RAM oreven the hard disk. There are many factors which affect how quickly the graphics card can do itsjob. Many of these only come into play when the graphics card is undertaking certain tasks.

Core clock speed -Much the same as the way you measure the speed of a CPU. The corespeed of the Graphics card is measured in MHz and represents the amount of clock cycles thegraphics process can do per second. This is a good but not definitive way of telling how fast thegraphics card is.

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Memory clock speed -Exactly the same of as the core clock speed, except of course that it isfor the memory of the graphics card and not the core. This is just as important as the core speedas the memory contains textures that need to be applied to the pixels.

Pixel Pipelines -The amount of pixel pipelines a graphics card has can have a great impact onthe speed of the image rendering. This is all about pixel pushing power. A card with 8 pipelines

can process twice as many pixels as a card of the same core speed and 4 pipelines.

Textures per pipeline -This only come into effect when multiple textures are needed on theone pixel. Simply put if a multiple texture is needed, then a graphics card with more textures perpipeline will be quicker. On single textured pixels the amount of texture per pipeline will have noeffect.

There are more smaller things such as T&L technology anti-aliasing and various other qualityincreasing and speed increasing technology that different cards have. I wont go into them allhere as there are a great many between all the cards on the market.

Memory Bandwidth

The memory bandwidth is the rate of data transferred from the GPU to the graphics memory.This has been one of the biggest bottle necks in graphics cards for years. Newer cards areovercoming this problem with expensive memory solutions at high speeds. The higher thememory bandwidth the better the graphics card will be able to retrieve data and textures fromthe graphics memory. As this is a real bottle neck this is a really important feature of thegraphics card