Laptop - Components

Components

The basic components of laptops are similar in function to their desktop counterparts, but are miniaturized, adapted to mobile use. Because of the additional requirements, laptop components are usually slower compared to similarly priced desktop parts. Furthermore, the design bounds on power, size, and cooling of laptops limit the maximum performance of laptop parts compared to that of desktop components.

The following list summarizes the differences and distinguishing features of laptop components in comparison to desktop personal computer parts:

• Central processing unit (CPU): Laptop CPUs have advanced power-saving features and produce less heat than desktop processors, but are not as powerful. There is a wide range of CPUs designed for laptops available from Intel (Pentium M, Celeron M, Intel Core and Core 2 Duo), AMD (Athlon, Turion 64, and Sempron), VIA Technologies, Transmeta and others. On the non-x86 architectures, Motorola and IBM produced the chips for the former PowerPC-based Apple laptops (iBook and PowerBook). Most laptops have removable CPUs, although some support by the motherboard may be restricted to the specific models. Some laptops use a desktop processor instead of the laptop version. Those laptops have high performance at the cost of being likely to have overheating problems, and having less battery life. In other laptops the CPU is soldered on the motherboard and is non-replaceable.

• Memory (RAM): SO-DIMM memory modules that are usually found in laptops are about half the size of desktop DIMMs. They may be accessible from the bottom of the laptop for ease of upgrading, or placed in locations not intended for user replacement such as between the keyboard and the motherboard. Currently, most midrange laptops are factory equipped with 3–4 GB of DDR2 RAM, while some higher end notebooks feature up to 32 GB of DDR3 memory. Netbooks however, are commonly equipped with only 1 GB of RAM to keep manufacturing costs low.
• Expansion cards: A PC Card (formerly PCMCIA) or ExpressCard bay for expansion cards is often present on laptops to allow adding and removing functionality, even when the laptop is powered on. Some subsystems (such as Ethernet, Wi-Fi, or a cellular modem) can be implemented as replaceable internal expansion cards, usually accessible under an access cover on the bottom of the laptop. Two popular standards for such cards are MiniPCI and its successor, the PCI Express Mini.
• Power supply: Laptops are typically powered by an internal rechargeable battery that is charged using an external power supply, which outputs a DC voltage typically in the range of 7.2– 24 volts. The power supply is usually external, and connected to the laptop through an AC connector cable. It can charge the battery and power the laptop simultaneously; when the battery is fully charged, the laptop continues to run on power supplied by the external power supply. The charger adds about 400 grams (1 lb) to the overall "transport weight" of the notebook.
• Battery: Current laptops utilize lithium ion batteries, with more recent models using the new lithium polymer technology. These two technologies have largely replaced the older nickel metal-hydride batteries. Typical battery life for standard laptops is two to five hours of light-duty use, but may drop to as little as one hour when doing power-intensive tasks. A battery's performance gradually decreases with time, leading to an eventual replacement in one to three years, depending on the charging and discharging pattern. This large-capacity main battery should not be confused with the much smaller battery nearly all computers use to run the real-time clock and to store the BIOS configuration in the CMOS memory when the computer is off. Lithium-ion batteries do not have a memory effect as older batteries may have. The memory effect happens when one does not use a battery to its fullest extent, then recharges the battery. Innovations in laptops and batteries have seen new possible matchings which can provide up to a full 24 hours of continued operation, assuming average power consumption levels. An example of this is the HP EliteBook 6930p when used with its ultra-capacity battery.
• Video display controller: On standard laptops the video controller is usually integrated into the chipset to conserve power. This tends to limit the use of laptops for gaming and entertainment, two fields which have constantly escalating hardware demands, and because the integrated chipset is very difficult to upgrade for a standard user, laptops may grow obsolete quickly for use in gaming and entertainment. Higher-end laptops and desktop replacements in particular often come with dedicated graphics processors on the motherboard or as an internal expansion card. These mobile graphics processors are comparable in performance to mainstream desktop graphic accelerator boards. A few notebooks have switchable graphics with both an integrated and discrete card installed. The user can choose between using integrated graphics when battery life is important and dedicated graphics when demanding applications call for it. This allows for greater flexibility and also conserves power when not required.
• Display: Most modern laptops feature 13 inches (33 cm) or larger color active matrix displays based on CCFL or LED lighting with resolutions of 1280×800 (16:10) or 1366 × 768 (16:9) pixels and above. Some models use screens with resolutions common in desktop PCs (for example, 1440×900, 1600×900 and 1680×1050.) Models with LED-based lighting offer lesser power consumption, and often higher brightness. Netbooks with a 10 inches (25 cm) or smaller screen typically use a resolution of 1024×600, while netbooks and subnotebooks with a 11.6 inches (29 cm) or 12 inches (30 cm) screen use standard notebook resolutions. Having a higher resolution display will allow you to fit more onscreen at a time, thus improving your ability to multitask. A higher resolution in a fixed size display will make items onscreen appear smaller than they would on a lower resolution. The difference between available display resolutions will often affect the user's experience considerably more than the difference between available processors and available memory, but it is commonly misconceived to be the opposite. 15.6" 1366 × 768 displays and 17.3" 1600 × 900 displays make items onscreen rather large, and tend to have poor image quality due in part to low contrast compared to their higher-resolution counterparts such as 15.6" 1600×900, 15.6" 1920×1080, and 17.3" 1920×1080, because the lower resolution displays are generally more cheaply manufactured. If you as a buyer have a budget that allows you to get a laptop that one of the higher-resolution displays and at the same time suits your needs, and if you don't require the larger text provided by a lower resolution for eyesight-related reasons, then it is commonly recommended that you avoid buying laptops that come with the lower-resolution 15.6" 1366 × 768 displays or 17.3" 1600 × 900 displays. 1366 × 768-resolution displays of sizes 14" and under tend to exhibit the same low-contrast-related poor image quality, but do not make items onscreen as large. 1600 × 900 resolution is occasionally available in sizes of 13.3" and 14", improving multitasking capability, but it is rare for such displays to have noticeably better contrast.

• Removable media drives: A DVD/CD reader/writer drive is nearly universal on full-sized models, and is common on thin-and-light models; it is uncommon on subnotebooks and unknown on netbooks. CD drives are becoming rare, while Blu-ray is becoming more common on notebooks.
• Internal storage: Laptop hard disks are physically smaller—2.5 inches (64 mm) or 1.8 inches (46 mm) —compared to desktop 3.5 inches (89 mm) drives. Some newer laptops (usually ultraportables) employ more expensive, but faster, lighter and power-efficient flash memory-based SSDs instead. Currently, 250 to 500 GB sizes are common for laptop hard disks (64 to 512 GB for SSDs).
• Input: A pointing stick, touchpad or both are used to control the position of the cursor on the screen, and an integrated keyboard is used for typing. An external keyboard and/or mouse may be connected using USB or PS/2 port, or Bluetooth (if present).
• Ports: several USB ports, an external monitor port (VGA, DVI, mini-DisplayPort or HDMI), audio in/out, and an Ethernet network port are found on most laptops. Less common are legacy ports such as a PS/2 keyboard/mouse port, serial port or a parallel port. S-video or composite video ports are more common on consumer-oriented notebooks.
• Cooling: Waste heat from operation is difficult to remove in the compact internal space of a laptop. Early laptops used heat sinks placed directly on the components to be cooled, but when these hot components are deep inside the device, a large space-wasting air duct is needed to exhaust the heat. Modern laptops instead rely on heat pipes to rapidly move waste heat towards the edges of the device, to allow for a much smaller and compact fan and heat sink cooling system. Waste heat is usually exhausted away from the device operator, towards the rear or sides of the device. Multiple air intake paths are used, because some intakes can be blocked, such as when the device is placed on a soft conforming surface such as a chair cushion. Some designs with metal cases, like Apple's aluminum MacBook Pro and MacBook Air also employ the case of the machine as a "gigantic" heat sink, and rely on it to pump heat out of the device core.Secondary device temperature monitoring may reduce performance or trigger an emergency shutdown if it is unable to dissipate heat, such as if the laptop were to be left running and placed inside a carrying case. Such a condition has the potential to melt plastics or ignite a fire.