All too often when a hardware technician first makes the move from fixing desktop systems to fixing his or her first laptop, it is hard not to feel a bit intimidated. After all, this is a laptop and not a regular computer! Laptops are different!
Well, I hate to be the one to break the news to you, but laptop computers really aren't that much different than their larger counterparts. They're just tinier is all. In fact, a vast majority of the technology that goes into the manufacture of portable computers has already been discussed in previous chapters.
Therefore, I'm going to start this chapter by reviewing material already covered that relates to portable computing before I dive into new material.
Laptop computers, as I said earlier, are nothing more than desktops with a hormone deficiency in most respects. They follow the same computer model that I introduced. Where they differ is in how the individual components are packaged. The figure shows just how many things fit under something as simple as the palmrest. Everything must be smaller, and where possible, designed to consume less power. When each individual component is designed to consume less power, then the overall system consumes less power. That means the battery lasts longer. And the one aspect in which laptops differ the most from desktops is in the fact that they frequently don't have the luxury of that little umbilical cord that attaches them to a power outlet in the wall.
With that in mind, I would like to spend the next few pages going over the basic components required by a computer system and discussing how they are designed differently for laptops. Where relevant, I'll also discuss commonly used methods of assembling laptops so that you will have a head start in figuring out how to take one apart.
In the early days of computing, up into the release of the first generation of Pentium by Intel, CPUs were almost universally designed to be 5V devices. As a result, early laptop computers (behemoths by today's standards) could only run for short periods of time between battery charges.
Intel first addressed this issue with the 80386SLC. This was a processor designed with portable computing in mind that operated on 3.3V. Since then, most CPU manufacturers have maintained separate lines of CPUs for desktops and notebooks. The CPU capabilities are similar, if not identical, but CPUs designed for portable computing are designed to consume less power.
Another difference that stands out is in how the CPU is mounted to the motherboard. Many designs featured a CPU that was soldered onto the main system board. In fact, some early models used a gold-plated tape to actually tape the processors into their sockets. That kind of put a crimp in the upgrading process. Most current designs allow the CPU to be swapped out, but you might have to get used to a different type of socket. Instead of the ZIF socket common to most desktops, many laptops incorporate Very Low Insertion Force (VLIF) sockets.
If you're looking for the release handle on one of these sockets, you can stop searching. In its place is a small screw. Turning the screw one way releases the CPU, while turning in the other direction locks it in place.
In Searching Your Memory, I discussed a memory package called the SO-DIMM (small outline dual inline memory module, in case your memory has failed you). Laptop manufacturers are by far the largest consumer of this particular memory package.
Generally, laptops will feature one of two designs. The first of these designs makes use of motherboards on which a base amount of memory is integrated right onto the motherboard. Then, for purposes of upgrades, one or two SO-DIMM sockets are provided. The second method is to simply put SO-DIMM sockets on the motherboard and ship the unit with one socket populated.
Upgrading or replacing memory on notebooks isn't any more difficult than it is on desktop systems. You just have to know where to look for the sockets. On some models, such as the one in the figure, you flip the laptop over and on the base of the unit is a small door held shut by a single screw. Remove the screw, pop the door open with a small flat-bladed screwdriver, and there are the sockets.
Other manufacturers weren't so friendly. On some models, the memory sockets are located underneath the keyboard. In order to replace or upgrade the memory, you must remove the keyboard. I'll discuss how you go about that a bit later.
The vast majority of laptops released today incorporate standard IDE drives in a 2.5" form factor. As you can see in the figure, these drives are much thinner that their 3.5" counterparts and consume far less power. The cable is typically a 2" 44-conductor cable, rather the 40 conductors used on desktop drives. The extra four conductors provide power to the drive. One conductor provides power to the motor, another provides power to the logic, and then there is a ground for each of them.
Changing out a hard drive in a notebook requires a bit more dexterity than does a desktop computer. In most cases, it is necessary to remove the keyboard, and in a few isolated models, the palmrest must come off as well.
Most laptop computers also offer the benefit of allowing the user to install hard drives in a PCMCIA slot (see Examining the Expansion Bus). These generally fit into a Type II slot and can be installed and removed as needed.
The one thing you won't see on a laptop computer is a CRT display. Wouldn't that be fun to carry around. Some of the very first "portable" computers were equipped with CRT monitors and weighed nearly twenty pounds. Not exactly unnoticeable weight to be carrying around, but for the professional in the field who needed a computer, it was a way to go.
Today's laptops all come equipped with one of the LCD displays I discussed in Your Computer and Graphics. While many earlier models of laptops sported passive matrix displays, these days even the cheapest models give the user the benefits of active matrix. These are of the TFT variety discussed in Your Computer and Graphics.
Because of the rough usage laptops are subjected to, their displays are all too frequently damaged or broken. While it's not an inexpensive part to replace, on a perfectly usable computer, it might be a less expensive option to replace a damaged LCD panel than to go out and buy a new computer. And on most models, it isn't all that complicated a repair.
With some models, the screen must be replaced separately and is a rather complex process that involves removing and disassembling the display. How you do this varies greatly from model to model. On most units shipping today, the display is an integrated component consisting of the display, the bezel, and the circuitry involved. A hinged bracket assembly usually holds this assembly in place. Two screws on the back of the computer (or on the bottom on some models) hold the display in place and the bracket slides backward away from the laptop. There are a few models that have additional screws on the bottom of the laptop that must be removed before the bracket can come out. But most have just those two screws.
The tricky part is not damaging the ribbon cable that interconnects the display to the motherboard. The terminals used are a bit different than the ones you get used to in desktop designs. They're actually a smaller implementation of the Sub-D assembly. The end of the cable slides into a slot on the motherboard. The slot is equipped with two tabs that lock the cable into place when pressed down.
Finally, there will be two other wires that need to be disconnected. These are the high voltage wires and generally coexist in a single plug-in terminal that makes removal and replacement an easy task.
The two most commonly seen removable media used by laptop computers are the floppy diskette and the CD-ROM. The key limitation to many laptop designs is the distinct lack of space for installing lots and lots of drives. Early on, one solution to this problem was to make the floppy and the CD interchangeable.
Here is another area in which PCMCIA shows its forte. Disk drives can be designed into PCMCIA Type III devices and then subsequently inserted and removed on the fly, as needed. Also, many manufacturers of laptops include a module bay that is used to swap out various devices, including floppy drives, CD/DVD drives, and even an extra battery if necessary.
Now that the review is out of the way, it's time to move on to some items you'll only see used in conjunction with laptop computers. Among these are the types of batteries used, AC adapter! chargers, PC cards, pointing devices unique to portables, and the docking station. Another device that deserves mention is a little toy called the port replicator. While it's true that most if not all of these devices see a certain degree of use outside the arena of portable computers, since it is with portables that they get the most exposure, this is where I've chosen to discuss them.
One of the key issues that had to be resolved when the first portable computers were developed was how to keep a constant and reliable supply of electricity available. A 250-mile extension cord didn't seem to be the answer, so batteries became the power source of choice. Some early models used standard alkaline batteries like you buy at the grocery store. When they were dead you put in some new ones and threw the old ones out.
This was neither cost-effective nor ecologically sensible. But rechargeable batteries of that era, like the one in the figure, were not very efficient for the purpose of laptop computers. The earliest of these batteries used an alloy of nickel and cadmium to generate and store current. These were called NiCad batteries and had a couple of rather serious inherent problems. The first of these was efficiency. It could take three hours of charging to give the batteries enough oomph to power a typical notebook computer of that time for half an hour. Second, NiCads exhibited a phenomenon called battery memory. Unless they were frequently discharged completely before recharging, they would "remember" how much of a charge they took in the last few recharging cycles and the amount of charge became its total capacity. The battery lost its ability to take a full charge.
Exam Note: Of all questions relating to portable computing, questions regarding the different types of batteries are the most common. Know your battery types.
NiCads were eventually replaced by Nickel Metal Hydride (Ni-MH) batteries. They really weren't a significant improvement over NiCads, but they helped a bit. While they still suffered from battery memory, it wasn't anywhere near as severe as it had been with NiCads. The recharge-to-usage ratio was a lot friendlier as well, giving slightly more usage time than it required to fully charge them. The most serious downside to Ni-MHs was that if overcharged, they could be permanently damaged.
Still, there was a lot of room for improvement. Today's notebooks all ship with Lithium Ion (Li-Ion) batteries. Li-Ions don't suffer from battery memory, you can plug them in for hours, or even days at a time and they won't overcharge, and it only takes about an hour of charging to get three to five hours of use.
The AC adapter/charger that ships with a particular unit will be specific to that computer/battery combination. Just because the connector tip of another adapter seems to fit your computer is not an indication that it will work properly. You could even destroy a notebook computer by using the wrong AC adapter/charger. If you examine the terminal that plugs into the computer, you see a small pin in the center, while the outside resembles a barrel. The pin is considered the tip. On adapters that output DC voltage, the adapter may be tip-positive or it may be tip-negative. What this means is that the tip is carrying either the positive or the negative current. Needless to say, they're not interchangeable.
Output voltages of different adapters also vary. A quick perusal of one online source of replacement AC adapters for notebooks turned up a range between 9V and 20V.
The PC card is basically another way of describing devices designed for the PCMCIA slots. While the PCMCIA bus was discussed in Examining the Expansion Bus, I have chosen to reserve a discussion of the cards themselves for this chapter. For the most part, PC cards are truly PnP. In general, they require no intervention on the part of the user as far as installation and configuration of a device, other than providing the driver disk when needed during the first installation of a new device.
PCMCIA slots are either Type I (3.3mm), Type II (5mm), or Type III (10.5mm). Type I and II slots are generally used for accessory cards such as NICs or modems. Type III slots see more use when designing drives.
One thing unique to PC cards is the typical structure of the device drivers used. PC cards use a two-tiered device driver. The first level is the socket driver. The socket driver notifies the computer when the device has been either inserted or removed and provides I/O operations. The second level is the card service. The card service interprets the command set for a particular device. As a result of this multitiered approach, PC cards can be added and removed on the fly as needed. However, before you simply start yanking devices out of your notebook, you might want to check with the manufacturer's instructions in this respect. There are some model-specific recommendations in this regard.
Exam Note: A good understanding of PC card drivers is useful even if you're not taking the exam. If you are planning to take the exam, it's essential. That's another popular subject.
The three most common pointing devices used on laptops are the trackpad, the trackpoint, and the trackball (discussed in Input Devices). The trackball is rarely used on modern computers and has already been discussed, so in this section I'll concentrate on the trackpad and the trackpoint.
Trackpads work by sensing the electrostatic energy generated by the user's finger. An array of transistors tracks the movement of the finger as it moves across the surface and relays vector information to the device driver. The driver converts this information into the data needed to display the mouse cursor in the proper position on the screen.
Because of this, The sensitivity of a trackpad is directly proportional to the amount of electrostatic energy emitted by the person using the computer. For example, if you have long fingernails, and try to operate the trackpad with the tip of a nail, in most cases, it won't work. A technician who has just finished servicing a laptop and is still wearing an antistatic wristband is often surprised to find that the trackpad either responds poorly, or not at all.
In general, the trackpad is part of the palmrest. A small ribbon cable that uses an LIF connector similar to the one used by the display connects to the motherboard. With some models, the trackpad can be replaced, if necessary, separately from the palmrest. With other models, it is necessary to replace the entire palmrest.
A trackpoint uses technology similar to trackballs, except that it is a scaled-down version, usually embedded in the keyboard. It is very small, operated by the tip of a single finger, and sports a textured rubber surface. These characteristics earned it the nickname eraser-point. The signals generated by the trackpoint are sent through the ribbon cable interconnected the keyboard to the motherboard. Should a trackpoint fail, it will be necessary to replace the entire motherboard.
Since many people dislike both trackpads and trackpoints, most manufacturers provide some way of hooking up a standard mouse or trackball to their models of laptop. This can consist of either a USB or a PS2 port. While this does add one more accessory to be carting around in the carrying case, many people find that minor inconvenience far less annoying than the inconvenience of fighting with one of these other devices.
More people are deciding that owning and maintaining two separate computer systems is more trouble than it's worth. (I don't know why! I have half a dozen!) Today's laptop designs are every bit as powerful as their desktop counterparts. The only drawback is that you can't install as many toys.
The docking station eliminates even that argument. The docking station is a device to which a portable computer is attached that allows full-sized components to be installed. A portable computer designed for docking station use will have an interface called a docking connector on the back of the computer.
Docking stations provide all the standard I/O connectors of a desktop computer and also allow additional drives and/or PCI cards to be installed that are not part of the o1riginal laptop's configuration. I went to Dell Computer Corporation's Web site and examined the specifications for one of its docking stations. It offers the following:
- Standard I/O ports installed include serial, parallel, video, two PS/2, four USB, VGA, DVI, S-Video, and audio ports
- One half-height standard PCI slot and one internal media bay with battery charging support
- RJ-45 and RJ-11 jacks for network and modem hookups
- Cable lock security with latch
This is not intended as a promotion for Dell's products, it is just an example of the array of options available. All notebook manufacturers offer similar options for their line of portable products.
One issue involved with using docking stations is the fact that the device list that the operating system must support changes between portable and docked configurations. This isn't really a problem, but each change does require that the OS detect and install drivers for the appropriate devices. This slows the boot process. The Windows user can get around this by creating a separate hardware profile for each configuration. In Device Manager, there is a tab called Hardware Profiles that allows you to copy the existing profile. You then highlight the devices unique to the docking station and for each of these devices select the option "Disable in This Profile". Save that profile as Portable and rename the original as Docked. The next time you boot the computer, you will be asked which profile you wish.
A port replicator is actually nothing more than a scaled-down docking station. In fact, with most models, the replicator attaches to the docking connector. A port replicator provides all the I/O ports of the docking station, but lacks additional PCI slots and/or drive bays. For many portables that lack integrated network support, it is usually possible to get a port replicator with a built-in NIC. As with docking stations, it is possible for the user to create separate profiles for each configuration to speed up the boot process
Exam Note: Another pair of devices that see their share of coverage on the A+ exam are the docking station and the port replicator. Know the differences between the two and the issues that arise when using either one.
The personal digital assistant (PDA) is a device that is currently enjoying tremendous popularity. While not a full-blown computer system by most people's standards, the PDA can take many day-to-day applications and put them in a shirt pocket. These applications include schedules, expense records, small database applications, and literally hundreds of others. Some models can interconnect to a cellular modem and allow for full Internet or networking capability while on the road.
Data is usually input with a stylus. The user opens the appropriate application and taps the surface of the display with the stylus. Text is usually entered in one of two ways. Some incorporate little teeny keyboards. The keys are depressed either with the tip of a fingernail or with the stylus if the user possesses sufficient coordination. Touch-typing is not much of an option. Other models bring up a display of a typical keyboard layout and the user taps the desired character with the stylus.
An emerging technology that has become incredibly popular is handwriting recognition. A popular implementation of this technology is called Graffiti. The user scrawls the message onto the space provided and the PDA converts it to text format. The problem that I see with that technology is that nothing exists that can recognize my handwriting. Not even my wife.
PDAs generally have their own specific and unique operating system. Currently the two most popular are the Palm OS, used by Palms, most Sony models of PDA, and many others, and Windows CE, used by many of the HP models as well as others.
Whichever way the user chooses to go, the PDA will offer some method by which he or she can interconnect the PDA to a standard PC and migrate data back and forth. Most PDAs also feature a slot into which external accessories can be connected. These accessories include memory cards, cellular modem hookups, and many others. As a technician, you probably won't see too many PDAs; they aren't really serviceable. When they die, generally the only option is to buy a new one.
Summary
- As you can see from this chapter, working with portable computers need not be intimidating. They're just smaller versions of the desktops you're already familiar with. The few differences that do exist are not technically challenging and are easy enough to understand and remember.
A+ Exam Objectives
Along the way, candidates for the A+ exam are going to see several objectives:
- Identify basic procedures for adding and removing field-replaceable modules for portable systems. Given a replacement scenario, choose the appropriate sequences.
- Determine the issues that must be considered when upgrading a PC. In a given scenario, determine when and how to upgrade system components.
- Recognize common problems associated with each module and their symptoms, and identify steps to isolate and troubleshoot the problems. Given a problem situation, interpret the symptoms and infer the most likely cause.
- Identify the types of RAM (Random Access Memory), form factors, and operational characteristics. Determine banking and speed requirements under given scenarios.
- Identify the most popular types of motherboards, their components, and their architecture. (Bus structures)
- If this list seems to induce a strong sense of déjà vu, that's probably because you've seen these same objectives over and over again. Here, I concentrated on how those objectives that related to portable computing.
Tricky Terminology
- Battery memory:
- A phenomenon exhibited by rechargeable batteries where the pattern of recent charge cycles affects the maximum charge the battery will accept.
- Card services:
- The portion of a PC card driver that interprets the command set for a specific device.
- Docking station:
- A device to which a laptop computer can be attached that provides additional hardware support, including I/O ports, PCI slots, and drive bays.
- PC card:
- Any auxiliary device designed to be plugged into a PCMCIA slot.
- Port replicator:
- A device to which a laptop computer can be attached that provides additional I/O services to the computer.
- Socket driver:
- The portion of a PC card driver that is responsible for I/O services and insertion/removal notification.
- Trackpad:
- A pointing device used on laptop computers that makes use of an electrostatically sensitive surface. The user runs a finger across the surface and the trackpad tracks the movement of the electrostatic charge.
- Trackpoint:
- A small pointing device used on laptop computers, similar to a trackball, but much smaller.
Acronym Alert
- Li-Ion:
- Lithium Ion. A type of rechargeable battery.
- NiCad:
- Nickel Cadmium. A type of rechargeable battery.
- Ni-MH:
- Nickel Metal Hydride. A type of rechargeable battery.
- PDA:
- Personal Digital Assistant. Any one of several computing devices designed for maximum portability.