Modern Portable Computer – Battery Technology, LCD Displays, Low-Power CPUs Report

Introduction

Laptops, palmtops, tablets and PDAs are computing devices that are being increasingly adopted for a variety of uses having an acute need of mobility while computing. These devices work with different hardware configurations than a conventional desktop computer and it is very important for any user of such devices to know about the technicals and working of the main hardware parts of these mobile computing devices in order to ensure uninterrupted and continuous usage. This paper focuses on the batteries, display and some power-saving CPU developments in the laptops of today.

Laptop Batteries

Batteries of the laptop are devices that enable a laptop to function without the main AC power supply. This working is supported for all laptop operations for anywhere between 1-4 hours depending upon the quality and the technology of the battery. A laptop like a desktop has CMOS & Clock Backup batteries which keeps u the date and the time when the laptop is turned off. This ensures that the restarted laptop carries on with the correct time and date. These are internal batteries of the laptop and these have another important function of saving the BIOS setup configuration, a program that is critically needed to reboot the system when restarted. Usually, the CMOS batteries are based on Lithium, Nickel Cadmium (NiCad) and alkaline technology and these are found fixed at one place on the motherboard. These batteries work with a current ranging between 3-7.2 volts.

Regarding the main laptop batteries, Wikipedia (2007) states as follows, “Laptops usually run on a single main battery or from an external AC/DC adapter which can charge the battery while also supplying power to the computer itself. Many computers also have a 3volt cell to run the clock and other processes in the event of a power failure [which confirms above narration]”. These main batteries have undergone rapid technology change and revolution over the years. Earlier alkaline, Lithium and NiCad batteries. While the former two were not chargeable and had to be replaced by equivalent new batteries; NiCad batteries were chargeable. An improvement over NiCad batteries came in the form of NiMH batteries (which was based on evolved and refined technology).NiMH batteries gave outputs of higher energy densities in comparison to NiCad batteries. For the same battery weight, a NiMH supplied twice the amount of power of a NiCad. This means that a leaner laptop can work for more hours with NiMH. NiMH batteries also do not have memory capture which means that NiMH clearly recognizes a full charge from a partial charge, unlike NiCads which were unable to distinguish this. Thus NiMH is more reliable and maintenance-easy. The latest development in battery technology is the Li-Ion battery technology. This has now become the benchmark battery technology. It has some advantages over the NiMH which the NiMH enjoyed over the NiCad batteries i.e. Li-Ion batteries have the same output as NiMH batteries but weigh nearly 35% less. This helps laptops turn leaner and less weight; in addition, Li-Ion batteries do not have any memory effect and are green products as they are not based on toxic chemicals such as Mercury or Cadmium. Random Access Memory (RAM) of some laptops are fitted with a backup battery which is a bridge or auxiliary battery. This makes the device switch on to such a battery in case the main battery fails. This helps the user with time to change the main battery as well as saves the settings and configuration. Frequently rechargeable NiCad or NiMH batteries are used as RAM backups. Smart batteries are equipped with chips that help them communicate with the laptop on battery performance, output voltage, temperature etc. These perform about 15% more than their non-smart counterparts. Kamal et al (2007) write about the latest development in battery technology, in a PowerPoint presentation at the Intel Development Forum, as follows, “High capacity battery technology has potential to High capacity battery technology has potential to support the vision of 8 hours of battery life-support the vision of 8 hours of battery life; fuel cell technology holds promise but vendors Fuel cell technology holds promise but vendors need to continue to pay attention to cost and form need to continue to pay attention to cost and form factor, and Intel AMPS allows support for new battery chemistries as well as fuel cells chemistries as well as fuel cells.”

The most critical power measurement used in relation to the laptop batteries is the Ah (Ampere hours) which can be then combined with the power consumption or power load of the laptop to calculate the run time of the battery. Several formulae have been devised to calculate such a run time. For instance, for a 12 v battery the following formula calculates the battery run time: (10 X (Battery capacity in Ampere hours))/ (Load Power in Watts)

Using the above formula one can calculate the run time of the chosen battery and go in for one or more batteries depending upon the requirements of computing. More battery cells simply augment the run time in any laptop as it improves the AH.

Laptop Displays and Energy-saving CPUs

The laptop is critically dependent on the quality of its display and the capability of such a display to handle high-resolution graphics that are based on substantial data. The display technology also interacts strongly with the power consumption of the laptop and thus affects the backup time of the battery. Keeping these aspects in mind the laptop display technology stabilized around two main streams.Wikipedia(2007) explains the history and technicals as follows, “By about 1991, two new colour LCD technologies hit the mainstream market in a big way; Dual STN and TFT. The Dual STN screens solved many of the viewing problems of STN at a very affordable price and the TFT screens offered excellent viewing quality although initially at a steep price. DSTN continued to offer a significant cost advantage over TFT until the mid-90s before the cost delta dropped to the point that DSTN was no longer used in notebooks. Improvements in production technology meant displays became larger, sharper, had higher native resolutions, faster response time and could display colour with great accuracy, making them an acceptable substitute for a traditional CRT monitor”.

The screen resolution is decided by the number of pixels a particular display is capable of handling. As Wikipedia (2007-i) explains, “A pixel (short for picture element, using the common abbreviation “pix” for “picture”) is a single point in a graphic image. The intensity of each pixel is variable; in colour systems, each pixel has typically three or four dimensions of variability such as red, green, and blue, or cyan, magenta, yellow, and black….. A pixel is generally thought of as the smallest complete sample of an image. The more pixels used to represent an image, the closer the result can resemble the original. The number of pixels in an image is sometimes called the resolution, though resolution has a more specific definition. Pixel counts can be expressed as a single number, as in a “three-megapixel” digital camera, which has a nominal three million pixels, or as a pair of numbers, as in a “640 by 480 display”, which has 640 pixels from side to side and 480 from top to bottom (as in a VGA display), and therefore has a total number of 640 × 480 = 307,200 pixels or 0.3 megapixels”.Similarly, all other screen resolutions can give out the pixels, in megapixels(one million pixels) which they can handle by simply multiplying the two measures of the screen resolution.. Recently LED-based LCD standardization is being attempted to improve the battery life and reduce the power consumed in laptop displays. As Kamal et al (2007-i) explain in an Intel Development forum presentation,” Reducing display backlight power is essential to extending the battery life of the platform”. They correlate the energy consumption with the display by reducing the statistics that the display subsystem(panel electronics, lighting system and the inverter) may consume anywhere between 33-40 % of the total power. They go on to explain that the new LED-based backlighting system will have the following major benefits in terms of energy saving, “ Support for thin and light form factor; RoHS compliant (mercury-free, lead-free); Low Voltage DC, no inverter; Vibration and shock resistant; Instant light on and off (less than 100 ns); Temperature range (-40 ????85°C); Luminance, uniformity & colour gamut same or better; Scalability; Easy LED driving & unlimited dimming, and direct CCFL replacement possible, no additional system cost!”

The above development had the parallel development in energy saving CPUs by major manufacturers like Intel. As Shultz (2007) explains, “The road to dual-core processors really began when Intel and AMD discovered that the goal of improving processor efficiency and performance by increasing the clock speeds towards the 3-GHz mark and beyond was actually having the opposite effect. The faster clock speeds were producing more heat and consuming more energy, both of which were hindering the efficiency and performance of the processors. Both companies realized that they needed to move towards dual-core processor technology in order to continue to improve processor performance. Dual-core processors contain two processor cores on one chip; consequently, they can simultaneously perform calculations on two streams of data, which increases efficiency and speed when running multiple programs. This is especially true when running new, multi-threaded software, such as video and audio editing applications” Shultz pinpoints the energy-saving aspect of the dual-core technology as follows, “In developing the Core brand of processors, Intel took the low heat and low voltage technologies developed for its recent mobile processor, the Pentium M, along with the EM64T 64-bit architecture technology, and combined that with its newly developed dual-core technology”.

References

1. Laptop. Wikipedia.(2007). Web.
2. Kamal Shah ,Shinichi Itoh,Will Hill &Calvin Shu.(2007).Laptop PC Power Sources:
3. An Update. Intel Development Forum.
4. Pixel. Wikipedia.(2007-i). Web.
5. Kamal Shah,Kevin Bosse ,K. Sugimoto,Bill Densham,Francis Nguyen, &.Ran Ghoman.(2007-i).LED As Laptop PC LCD Backlight: A Panel Discussion. Intel Development Forum.
6. Shultz,Greg.(2007).SolutionBase: Surveying the dual-core processor landscape. Web.