Also known as the CPU (Central Processing Unit), the processor is the brains of the computer. It's a particularly important chip in a notebook, because it has power-management features that extend battery life. The processor's clock speed, which is measured in megahertz (MHz) or gigahertz (GHz), tells you how fast your computer's microprocessor executes instructions. AMD's Mobile Duron and Mobile Athlon 4, and Intel's Mobile Celeron chips appear in budget notebooks; the Mobile Athlon XP and Intel's Mobile Pentium III-M and Mobile Pentium 4-M are found in performance notebooks. A third manufacturer, Transmeta, offers Crusoe processors that perform like Celerons and Durons but draw very little power, making them suitable for ultra-portables. Apple's iBook and Titanium PowerBook models use the PowerPC G3 and G4 processors, respectively.
Every computer comes with a certain amount of physical memory, usually referred to as main memory or RAM (Random-Access Memory). Computers store currently running applications and data in this area. It'll be a lot easier to choose notebook memory than desktop memory because most notebooks use SDRAM (Synchronous Dynamic RAM). To determine how much memory you'll need, you must take into account your operating system and the applications you plan to use. A general rule of thumb: you'll need at least 256MB for Windows XP or Mac OS X and 128MB for all other Windows and Mac operating systems.
This magnetic disk provides you with space to save programs and files indefinitely -- or at least for the life of the drive. The more disk space you have, measured in gigabytes (GB), the more data you can store. Notebooks currently top out at 60GB -- but these drives cost hundreds of dollars more than the default 20GB notebook drives. And because notebook drives must be smaller, use less power and absorb more shocks than desktop drives, notebook hard drives are slower and more expensive than their desktop counterparts. But capacity alone doesn't make a good hard drive. The hard disk's rotational speed also makes a big difference; a 5,400rpm notebook hard disk delivers significantly faster performance than a 4,200rpm model. The faster the disk spins, the better your notebook will perform overall.
This term merely refers to drives that read removable discs, such as CDs and DVDs. You need at least a CD-ROM to install software, of course. But unless you're buying a budget notebook, don't settle for anything less than a CD-RW drive. Since CD-RWs have the ability to read CD-ROMs as well as burn CD-Rs or CD-RWs, you can avoid buying a floppy drive if you want. For watching movies and playing high-end games on the road, consider a CD-RW drive that doubles as a DVD drive. You can purchase a notebook that comes with an optical drive or buy a drive separately. The least expensive notebooks come with fixed (built-in) drives, but a swappable drive bay gives you optimum flexibility. The smallest and lightest models may include neither, relying instead on external USB drives.
Notebooks ship with thin liquid-crystal displays (LCDs). Notebooks LCDs range in size from 12.1 inches (diagonal) up to a massive 17in. For comfortable viewing at 1,024 by 768 (the preferred Windows resolution), most people prefer 14.1in. or larger screens. Notebook LCDs used to vary widely in brightness, colour and sharpness, but today, you'll find much better quality across the board. Unfortunately, when it comes to LCDs, specifications reveal little about actual picture quality, so if you're picky about screens, try to compare some in the flesh.
Dimensions and weight
Whether you're buying a notebook to replace a desktop PC or just for carrying around, size and weight really matter. Like boxers, notebooks have weight classes, and with some exceptions, nearly all notebooks fall into one of four categories. Ultraportables weigh less than 2kg, measure between 2.5cm – 4cm thick, and have 12.1in. or smaller screens, no internal drives, and slower CPUs and hard drives (which draw less power). Thin-and-light models, which are just slightly larger and heavier, have 14.1in. to 15in. screens, a single drive bay and faster CPUs and hard drives. Mainstream notebooks aim to strike a balance between size, weight, features and power. They're heavier than smaller laptops, may include fixed drives, and typically offer the best value for tight budgets. Finally, desktop replacements are for those who care less about size, weight and price. These systems can weigh as much as 4.5kg but offer top performance, the largest displays and the most features.
Most notebooks have processors and memory dedicated specifically to graphics processing -- in other words, rendering text, images and video on your display. Although they still can't match desktops for graphics processing power, today's notebooks are capable of handling video, 3D games and high-end applications, thanks to advances from companies such as ATI and Nvidia. The amount of video memory a system has depends on the class of notebook: smaller notebooks may top out at 8MB, while desktop replacements offer 32MB or 64MB. Budget notebooks often lack their own video memory and instead borrow system memory. Gamers should look for an AGP (Accelerated Graphics Port) with a fast 4X bus -- the pathway between the graphics accelerator and the notebook's processor. For presentations and desktop use, make sure the VGA-out port supports monitor resolutions of at least 1,280 by 1,024 with 24-bit colour.
In order to send and receive email, browse the Web and share files or printers, your notebook must be able to connect to a network or the Internet. Virtually all notebooks come with 56Kbps modem (RJ-11) and Ethernet (RJ-45) connections. Look for a system that integrates these connections on a Mini-PCI card, leaving your PC Card expansion slot(s) free. Many notebooks also include built-in antennas for wireless networking (802.11b or Wi-Fi) so that you need only add a PC Card or a Mini-PCI card to enable wireless networking.
Ports and expansion options
Typically located on the rear or side panels of a notebook, a port is a connector that you use to physically connect other devices. Different ports communicate with different kinds of equipment. Most notebooks have a printer port, a VGA port for an external monitor, and at least one USB port for connecting external keyboards and mouse, drives, digital cameras and MP3 players. Most systems also have one or two Type II PC Card expansion slots, although these are no longer as essential now that most notebooks have built-in modem and Ethernet connectors. If you plan to use your notebook as a DVD player or for presentations, look for a system with a multimedia jack (combined stereo- and video-out). For home use, you may want a stereo input, a game port, a MIDI connector and a FireWire port for capturing and editing digital video or hooking up an external storage drive. If you can't find the port you want, you can usually buy a port replicator or a docking station; this adds connectors, room for more drives and cards, and the convenience of leaving cables plugged in when you walk away from your desk. Notebook expansion options tend to be pricey, so you're generally better off buying a notebook that has everything you need out of the box.
What good is a portable device without a battery? Not much. Notebooks now universally use lithium-ion batteries that deliver longer battery life and stand up to repeated recharging without any decrease in performance. Notebooks with greater performance and features require bigger, bulkier batteries to keep things running. Generally speaking, all notebooks -- regardless of size -- should deliver at least two hours of battery life, but preferably much more. Don't believe the manufacturer's rosy estimates of battery life; in real-world use, your battery life will be a lot shorter. ZDNet Labs' battery tests, included with all of our reviews, are more realistic estimates. Some notebooks can accommodate a second battery or a slice (an attachable base), which will provide enough power for mid-haul aeroplane flights.
Service and support
If anything goes wrong with your notebook, you'll need a lengthy and comprehensive warranty, backed by knowledgeable and convenient technical support. Most manufacturers provide at least a one-year warranty on parts and labour, while a few still include warranties that last as long as three years. But not all warranties are equal. Look for one that includes on-site service (when a technician shows up at your door), or at least covers the cost of shipping to and from the service centre for repairs. Some warranties also guarantee to repair your system or provide a replacement within a few days. The best support plans provide 24-hour, 7-day help via toll-free telephone and email, as well as online resources such as FAQs (Frequently Asked Questions), user manuals, downloads, discussion forums and even live online chats with support technicians.