Hardware specifications
GOOD DAY, students. This is lesson seven in our lessons. In this week’s lesson, we will be looking at hardware specifications and terms associated with storage devices. At the end of this lesson, you will be able to define key terms associated with storage, such as ‘tracks’ and ‘sectors’, identify different storage capacities of a hard drive or main memory (RAM), and determine the speed of a given processor.
Whenever you decide to buy a new cell phone, laptop or even a desktop computer, one of the first things you will consider and will ask the sales clerk about is the ‘specs’? In other words, you will ask what are the storage capacity, memory size and speed of the processor.
THE PROCESSOR
The processor is measured by its clock speed in megahertz (MHz) or, most recently, in gigahertz (GHz). The faster the clock speed of the processor, the faster is the execution of an instruction, task or command you give the computer. Examples are shown below of a few processors and their respective speeds. Intel (R) Pentium (R) CPU B970 @ 2.30 GHz Pentium 4 processor 540 w/HT technology @ 2.8 GHz AMD FX 4-Core Black Edition @ 3.8 GHz
MEMORY
When we refer to random access memory/main memory, we do not necessarily speak about what speed it is measured in but rather its size. The size of RAM can be measured in megabytes (MB) and gigabytes (GB). There are two main types of RAM: dynamic RAM (DRAM) and static RAM (SRAM), but you may also see a combination called SDRAM. Similar to the processor’s clock speed, it is better to have more memory, as the better the memory, the better the performance of your computer. Examples are shown below of three types of memory and their respective sizes. 2GB DDR2
4GB DDR3 SDRAM
8GB DDR4
Note: DDR means double/dual data rate.
HARD DISK DRIVE (HDD)
In comparison to RAM, main memory processing speed is faster than the hard drive. Information is generally swapped between main memory and the hard drive. The size of a hard drive is measured in gigabytes (GB) and more recently in terabytes (TB), and the larger the hard drive capacity, the more data and information can be stored.
Access time for the HDD is measured in milliseconds (ms) and its speed, which is the revolutions per minute (RPM), ranges from 5,400 to 12,000 RPM. The two main types of hard disc drives are IDE hard drives and the SATA hard disc drive, which is determined by the device interface cable that they use. The hard drive you will likely to purchase now is the SATA hard disc drives. Examples of hard disk drives and their respective sizes are shown below.
500GB SATA hard disc drive (5,400RPM)
3.0TB SATA hard disc drive (10,000RPM)
Let us now look at some key terms associated with storage devices.
TERMS ASSOCIATED WITH STORAGE DEVICES
Before we look at the terms associated with storage devices, let us first look at how data is stored on a disc.
FLOPPY DISC
Data is recorded on a thin, circular, plastic disc, coated with magnetic material. Like other magnetic discs, the disc must be formatted (prepared) or divided into areas (tracks and sectors) before data can be read or written to it. Without formatting, there would be no way to know what data went with what. Thus, in formatting your diskette, your files can be placed in an organised fashion.
TERMS
1. Track: A track is a concentric circle on the disc where data is stored. On a disc, there are 80 tracks on each surface top and bottom. The blue-shaded portion of Figure 1 (shown below) is an example of a track.
2. Sector: A sector is a pie-shape part of a track. Data is recorded along a track within a sector. Each track sector is identified by a unique address so that every recording location can be identified.
3. Cluster: A cluster is a set of track sectors, ranging from two to 32 or more, depending on the formatting scheme used.
4. Cylinder: A cylinder is similar tracks on a platter of disc.
Below is a diagram (Figure 1) to illustrate some of the terms defined above.
READ/WRITE HEAD
This is a device that reads data from, and writes data on to, a storage media. (You were introduced to this term in the previous lesson, but it is now being highlighted as one of the key terms associated with storage devices.)
MOVABLE HEADS DISC DRIVE
These are disc drives that have one read/write head for each surface. The access arms move in and out in order to access the desired track.
FIXED HEAD DISC DRIVE
These are disc drives that have one read/write head per track. Therefore, if a disc pack has 10 tracks, then each surface would have 10 read/write heads. This reduces the time needed to access records in a particular sector on a track. Figure 2 shows the location of the read/write head alongside its corresponding arm(s).
ACCESS TIME
After formatting the disc, the read/write heads need to access the stored data in as short a time as possible. Heads are mounted on access arms that are positioned between the platters. The access time of a read/write head depends on the following:
1. Seek time, which is the time taken to move the head to the particular track.
2. Rotational delay, which is the time it takes the disc to rotate to the particular sector.
We have come to the end of this lesson. See you next week. Remember, if you fail to prepare, you prepare to fail.