Sim-Ex™ Tutorial for A+ Essentials

2.0 Laptop and Portable Devices

2.1 Identify the fundamental principles of using laptops and portable devices

Identify names, purposes and characteristics of laptop-specific:
- Form factors such as memory and hard drives

A laptop computer is primarily intended to be portable. The characteristics of a portable device are given below:

Lesser weight: People prefer to carry a laptop that weights, say 5lb (approx. 2 kg) than one that weight 20lb (or 8 kg). A laptop typically weighs less than 10 lbs compared to a typical desk top that weighs about 20lbs.
Lesser power consumption: laptops consume much less power compared to desk tops. Typically, a DC converter is used to feed DC power to a laptop computer. The DC converter converts the AC power (US:110V, EU:220V) to required DC voltage. An internal battery supplies power to the laptop when there is no AC power available.
Rugged: All the components of a laptop are ruggedized to enable safe transport from one place to another. A laptop consists of smaller form factor assemblies that are ruggedized for both heat and vibration. We will be discussing the sub-assemblies form factor at a later stage.
Slim display: Usually all laptops have integrated LCD (or TFT) display as compared to desk tops that have CRT displays. CRT displays are bulkier and consumes more energy.
Integrated Keyboard and Mouse: A laptop has integrated keyboard, and mouse. However, it is possible to connect external mouse and keyboard for convenience on most of the laptops.

Functionally, there is no difference between a laptop and a desktop computer. Both run same operating systems, and applications.

We now discuss the said characteristics of laptops in more detail:

1.Laptop memory:

Laptops widely use SO-DIMM (Small Outline Dual In-line Memory Module), a smaller version of regular DIMM components used in desktops. The figure below provides a comparison of SO-DIMM and a regular DIMM package:

As can be seen from the above figure, a SODIMM is roughly half the size of a regular DIMM used in desktop computers.

SDRAM (Synchronous Dynamic Random Access Memory) has a synchronous interface. It waits for a clock pulse before transferring data and is therefore synchronous with the computer system bus and processor. This greatly improved performance over asynchronous DRAM. Notebook SDRAM modules are usually 144-pin SO-DIMMs, as shown in fingure above.

DDR SDRAM (DDR stands for Double Data Rate) sends and receives data twice as often as SDRAM. This is achieved by transferring data on both the rising edge and the falling edge of a clock cycle. DDR memory usually comes in the form of a 200-pin DDR SO-DIMM (see image above).

Second generation DDR memory provides greater bandwidth and works on a voltage of 1.8V instead of the 2.5V used by DDR memory modules, DDR2 consumes less power than its predecessor, helping to extend notebook battery life. DDR2 memory modules are 240-pin DDR2 SO-DIMMs.

Memory Speed: Two factors are used for this measurement. 1. The operating frequency and 2. the bandwidth. SDRAM rated PC100 and PC133 work at 100MHz and 133MHz and provide 800MB/s and 1066MB/s bandwidth respectively. SDRAM and DDR/DDR2 SDRAM all use 8-byte (64bit) wide DIMM (transfer 8-byte data per clock cycle).

DDR and DDR2 memory uses different notation. DDR266 memory works at 266MHz, providing 2100MB/s bandwidth (Corresponding to the PC2100 designation). DDR400 memory is called PC3200 for its 3200MB/s bandwidth. The DDR2 533 is also called PC2 4200 or PC2 4300 but 'PC2' is used here to refer to DDR2 instead. DDR2 800 is the same as PC2 6400.

The bandwidth above is for single channel use. When memory is used in dual channel mode, the bandwidth doubles - for instance, dual channel DDR400 provides 6400MB/s (or 6.4GB/s) bandwidth as opposed to 3200MB/s for single channel DDR400.

Recommended Laptop Memory Size:

Mainstream Users: 512MB or more

A capacity of 512MB is the minimum required to run multiple simultaneous current-day programs. A capacity of 256MB can sufficient for everyday applications such as Web surfing, chatting, and office work.

Business Users: 1GB or more

If you often open and work on many large documents simultaneously, a memory of 1GB is recommended for faster switching between applications as most application data is stored in RAM instead of being accessed from the hard drive every time it is needed (relatively slow).

Multimedia Users/Gamers: 1GB or more

A memory of 1GB is the recommended minimum if you play any latest games. For multimedia processing tasks, which are similarly resource intensive, a memory of 1GB is recommended.

Mobile Workstation Users: 2GB

Professional developers require as much memory as possible. Typical applications involve image processing, video/audio editing, etc. A memory of at least 2GB memory is recommended for smooth performance.

2. Laptop Hard disks:

Laptop hard disks primarily differ from that of desktop hard disks in size and reliability. Given below are the important characteristics of laptop hard disks:

Small form factor : A desktop computer has 3.5-inch drives, whereas a notebook computer, on the other hand, has a smaller 2.5-inch or 1.8-inch notebook hard drive. 1.8� hard drives are mainly installed and used in ultra-portable notebooks.
Low power consumption : Like other notebook components, hard drive is specifically designed for reduced power consumption. The average operating power consumption of a 7,200 RPM 3.5-inch internal hard drive currently exceeds 10 watts. A typical 7200 RPM notebook hard drive consumes about 2 watts by comparison.
Silent Operation : Though current notebook hard drives spin at speeds of up to 5,400 RPM and even 7,200 RPM, the noise-reduction technologies employed in current hard drives mean that hard drives can run quetly.
Enhanced reliability

Quite unlike desktop computers, notebook computers are often moved from one place to another. To this end, enhanced vibration and shock protection are important for laptop hard drives. A typical notebook computer hard drive can take more than double the shock/vibration to that of a desktop hard drive.

Important specifications are given below:

Capacity : Notebook hard drives offer capacities of over 100GB. Hard drives of capacities 20GB, 40GB, 60GB, 80GB, 100GB, 120GB, 160GB and 200GB models are all available.
RPM : The spindle speeds determines the performance of a hard drive. Most of the notebooks have hard drives with 5,400 RPM. Other available speeds include 7,200 RPM and 4,200 RPM drives. A 7,200RPM provides better performance (at more power consumption), and a 4,200 RPM hard drive consumes less power but offers slower performance level.
Cache : Hard drive cache helps to improve the performance by holding the data temporarily for rapid access. A larger cache is recommended for better performance of a hard drive. Notebook hard drives typically come with 2 MB, 8MB or 16MB cache options.
Interface : Two interface standards available with notebook hard drives are: 1. parallel ATA (also known as IDE) and 2. serial ATA (known as SATA). Most parallel ATA notebook hard drives follow the ATA-6 specification for 100MB/s I/O throughput. SATA notebook hard drives follow SATA 150 for a throughput of 1.5 Gb/s (150MB/s), or SATA 3.0 Gb/s for a throughput of 3.0 Gb/s (300MB/s).
Form factor : Two notebook hard drive form factors widely used are: 2.5-inch and 1.8-inch. The former is widely applied in most notebook types, while the latter is typically found in ultra-thin notebooks. The thickness of hard drives may differ. Therefore, even if you find a 2.5 inch hard drive is recommended for your laptop, ensure that the thickness of the hard drive is also complying the specified value. For example, a 2.5-inch hard drive with a thickness of 12.5 mm is not suitable if your notebook will only hold a 2.5-inch hard drive that is 9.5mm thick.

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