Different Types of Portable Computers and Their Specifics

Before you start

Objectives: learn about different types of portable computers, about their specific design, typical expansion slots that they use, different types of batteries that are used, about power management, and typical ports.

Prerequisites: no prerequisites.

Key terms: battery, notebook, system, type, power, pcmcia, portable, card, laptop, port, expresscard, memory, nicad, external

Types of Portable Computers

Notebook computers and portable devices are examples of portable computers. There are several different types of mobile computing devices. A notebook (or laptop) is a portable version of a desktop system. It often has similar hardware and runs similar software.

In addition to laptops we also have a Personal Digital Assistant, or PDAs. PDAs are also sometimes called palmtop computers or handheld computers. Typically PDA has a small touchscreen. With a PDA we don’t have to use a keyboard. Instead, we use optical character recognition. With a little stylus we can write on the screen. A stylus is a special pen designed to be used by these touchscreens for input. The processor inside the PDA interprets written text and displays it on the screen as characters. A PDA uses special hardware and software that provides basic productivity applications like e-mail, word processing and spreadsheets.

In addition to PDAs, there’s also a hybrid type of portable computer that has become very popular and it’s called a tablet PC. A tablet PC is a fully functional notebook PC. However, they have a screen that operates in much the same manner as a PDA. A touchscreen allows input by tapping on the screen, dragging objects, or through handwriting recognition. Tablet PCs might run special versions of the operating system to enable touchscreen input.


Portable devices are built to be lighter and easier to carry. Components are placed in closer proximity and are engineered to minimize the power consumption because portable computers often run on battery power. Because the devices are built to be carried around, they also must withstand more wear and tear.


Processors built especially for laptop computers have lower power consumption requirements and produce less heat than desktop processors. On some portable systems we can configure the processor to use a lower bus speed when running from battery power, thereby conserving battery life. Many mobile processors are capable of automatic throttling to turn off extra cores or reduce the speed to conserve energy. Processors do not have the large heat sink and fan combinations to dissipate heat. Heat is controlled by minimizing power consumption and small fans that draw away heat.


Laptop memory uses SODIMM packages with SDRAM, DDR/DDR2/DDR3, or RAMBUS memory. These modules are sometimes called MicroDIMMs. Many notebooks come with a base amount of memory built onto the motherboard and one or two additional slots.


Notebook keyboards are smaller than standard keyboards. Keys are often a bit smaller and closer together. Keys such as the number pad and some function keys might be left off, but are accessible by pressing a special Fnkey to provide alternate functions for regular keys. We can use a USB port to connect an external keyboard, and some older laptops include a PS/2 port to do the same thing.

Pointing Device

Instead of a mouse, notebooks can use pointing sticks, which are small knobs in the center of the keyboard. Pushing on this knob moves the cursor. Most laptops will have touchpad which is located below the keyboard. Moving finger across the pad moves the mouse. We can also tap the touchpad to click the mouse. Notebooks with a pointing stick often come with a touchpad as well. Buttons below the keyboard replace mouse buttons for clicks, double-clicks, and right-clicks. We can also use USB to connect an external mouse. We can also use a digitizer pad to receive input. Input is written onto the pad with a stylus pen, then those motions are transferred into data that is processed by the system.


The video controller is either integrated onto the motherboard or it might be a separate board that can be replaced. Video memory typically shares a portion of the system memory, although some notebooks have dedicated video memory. Most notebooks have an external video port that we can use to display the screen on a projector or a monitor.


Most laptops include built-in networking devices such as an Ethernet port, a modem port, wireless, Bluetooth, and/or infrared. Wireless networking is often provided by a small card that plugs into an internal mini-PCI slot which is located under the keyboard or accessible through the back. The wireless antennae might be a wire that extends around the screen. If we miss those features, we can use USB or PCMCIA cards to add those.

Long Term Storage

Internal hard disks are typically 2.5″ and very thin compared to desktop hard disks. PATA, SATA, and increasingly solid state drives are used in portable devices.

Typical Expansion Slots

The first typical expansion bus that we will mention is Personal Computer Memory Card International Association Expansion Bus, or PCMCIA.


The PCMCIA expansion bus uses expansion boards called PCMCIA cards, sometimes called PC cards. PC Cards come in a number of configurations with varying characteristics and functions. They look like a credit card, and they slide into a slot in the notebook system to connect to the 16-bit or 32-bit host I/O bus on the motherboard. They can provide functions like wireless network card, USB adaptor, modem, CD-ROMs, sound cards, SCSI host adapters, FireWire controllers, and all kinds of other peripherals.


338.1 – PCMCIA Slot

There’s actually several different types of PCMCIA cards. The first type is the Type I. Type I cards were 3.4 inches (8,6 cm) by 2.1 inches (5,3 cm) and they were 3.3 millimeters thick. Type I cards were used for memory /such as SRAM and Flash), but now are obsolete. A Type II card has the same dimensions as a Type I card. The difference is that it’s 5 millimeters thick. We will often find two Type II PCMCIA slots on one system. Type II cards were used for I/O, such as modem and LAN. In addition, there’s a Type III PCMCIA card. A Type III card has the same dimensions of a Type II with the exception that it is 10 millimeters thick. Type III cards were used for mass storage like hard drives ans optical drives. If we use a Type III card it uses up both Type II slots in a notebook system, but actually has one connector inside. So, dimensions for all PCMCIA types, excluding thickness, are the same, and each card type has a 68-pin connector. Thinner cards fit into the thicker ports, but not vice versa. For example, a Type I card will fit into Type II and III ports while a Type III card requires two Type II ports. Note that PCMCIA standards are replaced by a new standard called PCI Express or ExpressCard.


338.2 – PCMCIA Type II


ExpressCard slots are connected directly to either the PCIe bus or to the USB bus. ExpressCard offers speeds up to 2.5 gigabits per second if we’re connected to the PCIe bus, or up to 480 megabits per second if we’re connected to the USB 2.0 bus. ExpressCards come in two different widths. Slots are either 34 millimeters wide or 54 millimeters wide. Therefore we have two different ExpressCard form factors to accommodate those two different slots. We have ExpressCard 34 which uses rectangular cards that are 34 millimeters wide. An ExpressCard 34 card can be used in either the 34 millimeter slot or the 54 millimeter slot. ExpressCard 54 cards are L-shaped cards that are 34 millimeters wide to fit into the slot, but 54 millimeters wide on the outside edge, so those cards fit only into 54 millimeter slots. When inserted into the appropriate slot, the ExpressCards will use either the PCI express bus or the USB bus, depending upon how the system is configured. ExpressCards can be used for all different types of devices, just like PCMCIA cards. ExpressCard can even be used to add a graphics card to out laptop to attach an extra monitor. Newer laptops often don’t have ExpressCard or PCMCIA slot. In that case all external devices will connect through the USB port instead.


338.3 – ExpressCard 34


To make the system truly portable, it needs to run on a battery. Notebook systems are designed to use as little power as possible. Notebook systems save power by turning off any drives that aren’t currently being used, stepping down the bus speed in the CPU, turning off the monitor after a period of inactivity, putting the computer to sleep or turning it off automatically. We need to understand that a computer system, whether it’s a desktop system or whether it’s a notebook system, must have a power source that supplies a constant voltage. When our laptop is plugged into the wall, it is receiving power through an adapter that converts the AC power from the outlet to DC power usable by the computer. Most adapters can be used on both 110 and 220 AC volt power sources. The energy received through the adapter is divided between running the notebook system and charging the battery. Remember that most adapters are not interchangeable between laptops because laptops require varying amounts of voltage and amperage and also have different plugs. Wrong adapter can cause a laptop to receive insufficient power to turn on, receive insufficient power to charge the battery or receive an excess of power that will fry the system. When a laptop is not plugged into the wall, it receives its power from the battery. Batteries wear out over time so we should expect to replace our battery every few years. We should never let a battery run extremely low because the life of a battery significantly decreases if it loses all of its charge. We can’t use ordinary batteries in our laptop since they lose voltage, they get weaker and weaker. That won’t work with a PC system. For a PC system to run we have to have a constant power source that supplies a constant voltage. To do that, we have to use a special type of battery. There are three different types of batteries that are commonly used with portable systems.

Nickel Cadmium Battery (NiCad)

The first type of battery is the nickel cadmium or the NiCad battery. This was the first type of battery that was used primarily in the older laptop type of portable computers. NiCad batteries had some problems. First of all, they suffered from a memory effect. Memory effect causes batteries to hold less charge. Batteries gradually lose their maximum energy capacity if they are repeatedly recharged after being only partially discharged. The battery appears to “remember” the smaller capacity. So, with a NiCad battery we had to completely drain the battery every time we used it to avoid the memory effect. Also, NiCad batteries had a relatively short life, and they were intolerant of high temperatures. If we got a NiCad battery too hot, they stopped working. They also take up more space than Li-Ion batteries. Another problem with NiCad batteries is that they were intolerant of being overcharged. If we overcharged them, we would damage them. NiCad batteries were made up of some highly toxic materials, so it was hard to dispose of this type of battery.

Nickel Metal Hydride Battery (NiMH)

The second generation of notebook battery was called the nickel metal hydride battery. It was a great improvement over the NiCad battery. First of all, it could last about 40% longer, as compared to a NiCad battery. In addition, it held a greater charge capacity than a NiCad battery. They didn’t develop the memory problem that NiCads did. If we overcharged it, it wouldn’t stop working the way a NiCad did. In addition, the materials used in the nickel metal hydride batteries were less toxic than those used in a NiCad battery. However, they were slightly more expensive than Nickel Cadmium.

Lithium Ion Battery (Li-Ion)

The newest type of notebook battery is called the lithium ion battery or Li-ion. A lithium ion battery has twice the capacity of a comparable NiCad battery. It doesn’t have the problems with memory effect the way NiCads did. It can’t be overcharged, and it isn’t as susceptible to heat issues like NiCads were. It has increased stability and safety. They take up less space and weigh less than NiCad or NiMH for comparable power output.  The only problem with lithium ion batteries compared to nickel metal hydride is that they have shorter lifespan and are more expensive.

Fuell Cell

New technology that is still developing. This is not actually a battery but it offers power like batteries do. Rather than being recharged which can take hours, the fuel is simply replaced using replaceable cartridges.

Batteries contain dangerous and regulated chemicals. We should always dispose of batteries according to the manufacturer’s directions. Disposing of batteries improperly might also be illegal in some countries.

Docking Station

Notebook systems now can compare with a desktop system when it comes to speed and the amount of memory. The fact that they’re portable makes them very useful. Many users are using only notebook system only. Docking station makes this more functional. Docking station is sometimes also called a port replicator. With docking station we can connect our notebook to a larger monitor, keyboard, mouse, wired network connection, DVD drive, speakers and other things as well. Well, usually we can find those ports on our laptop, but the nice thing about a docking station is the slide-in, slide-out function. If we want to use it as a desktop system, we slide it into the docking station. When we’re ready to take the notebook home after work, we slide it out and it’s all ready to go.

Dell PR01X

338.4 – Docking Station Example

Notebook Ports

Different notebook manufacturers use different arrangement of different external connectors. They might not even include some of the external connectors. Almost every notebook system will have the fans that are used to cool the CPU, the RAM and other components inside the notebook case. We will also have the power connector, which it’s used to connect our PC system to a transformer which is in turn connected to our 110 volt (220 volt in EU) wall outlet. On older laptops we will also find a PS2 mouse or keyboard connector (mini din connector). Sometimes we will have one PS2 connector which we can use  for either one or both. We can purchase a special adapter that has one mini din plug that we attach to the laptop and then it splits to one connector for the keyboard and one connector for the mouse. Most laptops will have video out port. We can use it to connect to an external desktop monitor. To see how those ports look like be sure to check out our article on typical computer ports.

The next connector is the docking bay connector (port replicator connector). Docking station allows us to easily unplug our laptop from an external mouse and keyboard, external video monitor, etc. When we need to use those external devices again, the port replicator allows us to simply slide the notebook system into a docking bay which is already connected to the monitor, keyboard, etc.

Older notebooks had a parallel port which was used to connect the notebook system to a parallel printer. The same thing is with serial port, we won’t see them any more on notebooks. The serial port was used for serial printers, modems, mice, etc.

What we will see on most notebooks today are USB connectors. With USB connectors we can also use external USB hubs which we can use to connect external devices as well. To have an article in which you can read about USB in detail.

Most notebook systems will have an integrated network interface. The network interface is an RJ45 jack which allows us to connect to an Ethernet twisted pair network. In addition most newer notebook systems also include an integrated wireless network interface, and the antenna is usually hidden into one of the sides of the display. It provides a wireless interface to connect to a wireless network. Older systems also include a modem interface, which we can use to connect an RJ11 plug to the notebook and to a telephone jack and dial up to an ISP. Some laptops will also include an infrared interface which allows us to send and receive infrared data.

Some laptops will include a mini FireWire port labeled 1394 so we can connect the notebook system to a FireWire device such as an external hard drive or digital camera. We have an article with more details about Firewire. Notebooks will also have audio connectors, typically microphone jack, headphone jack and line in jack.

The port which was really important for notebook systems in the past is the PCMCIA slot. The PCMCIA standard was replaced by PCI Express, or Express Card. On the picture below we have an ExpressCard 34 and ExpressCard 54 side by side. When comparing with PCMCIA, we can see that the width of the card is narrower.


338.5 – ExpressCard Form Factors

Some notebook systems provide removable drive bays. For example, CDROM drive or a DVDROM drive can be removed from the system and replaced by other drive. For example, we can insert a floppy disk drive instead of DVD drive, if we have some important diskette that we have to read.

Some older laptops had S-Video port, which was used to output video signal to our TV. Newer systems will have HDMI port or DisplayPort to do the same thing. We have a separate article in which we discuss different video ports.

Portable devices typically do not have free internal bus slots that we can use to add components to the system. Instead, components are typically added using removable drive bays, USB or Firewire ports, PCMCIA and PCI Express (ExpressCard) card slots. Most external laptop components are hot swappable. We have to make sure to use Safely Remove Hardware before removing a hot swappable component. Also, we have to keep in mind that using additional devices with our laptop system can increase heat output and discharge the battery faster.


A notebook (or laptop) is a portable version of a desktop system. A PDA uses special hardware and software that provides basic productivity applications like e-mail, word processing and spreadsheets. A tablet PC is a fully functional notebook PC. Portable devices are built to be lighter and components are engineered to minimize power consumption. Typical laptop expansion slots are PCMCIA and ExpressCard. Portable computers run on battery which can be Ni-Cad, NiMH, and Li-Ion. Docking stations allow us to use our laptop as desktop PC.