PC Cards and Power

Objectives:

To introduce the history and development of portable computers

Discuss the development of portable computers

Discuss PC cards and power management

Lesson:

A Personal Computer Memory Card International Association (PCMCIA) - or PC - card
is a memory or I/O device the size of a credit card that connects to a notebook
or laptop computer.

PC cards are capable of performing most computing functions.

Modems are a common use for PC cards in portable computers.

PC cards are inexpensive and easy to use.

And all PC cards connect to the computer using a 68-pin interface.

There are three different PC card types based on the thickness of the card - Type
I, Type II, and Type III.

Type I is 3.3mm thick and commonly used for flash memory.

Type II is 5.00mm thick and used for I/O functions, such as modems, LANs, SCSI,
and sound.

And Type III is 10.5mm thick and used for hard drives.

Type II cards are the most frequently used type, so most portables are fitted with
two-tiered Type II slots.

This configurations allows for the hosting of two Type I or Type II cards, or one
Type III card.

Two levels of software drivers support PC cards - lower level and higher level.

Lower level drivers consists of a set of drivers known as socket services, which
the system uses to detect the presence of a card.

These socket services also provide input and output functions for the card.

Higher level drivers, known as card services, supply the correct drivers for the
PC card currently inserted.

With earlier laptops, each manufacturer provided drivers specific to the laptop.

However, this meant that you couldn't use any PC card in any brand of laptop.

This problem was overcome by standardizing socket services.

The most recent development in PC cards is the cardbus.

While other PC cards are 16 bit, the cardbus is a special 32 bit card, which can handle Peripheral Component Interconnect (PCI) bus mastering.

This allows a single PC card to have up to eight functions, such as a network card,
a modem, and sound.

The cardbus has the same number of pins and the same physical dimensions as an ordinary PC card.

You can insert standard PC cards in a cardbus slot, but you cannot insert a cardbus in a PC card slot.

The operating system prevents this explicitly because standard PC cards use a higher voltage than cardbuses.

Also, you cannot use a cardbus unless the portable is running Windows 95 OSR2 or a later version.

When portables were first developed, components such as the screen and the hard drive did not switch off automatically when not in use.

Using power management, the user can configure components to shut down after specified
intervals of inactivity.

Systems that have power management capabilities depend on specialized hardware.

Advanced Power Management (APM) requires a CPU capable of System Management Mode
(SMM).

The BIOS needs to be APM-compliant so that the CPU can send APM commands to peripherals.

In addition, peripherals need to be Energy Star peripherals, which can be configured to shut down without switching off.

There are four levels of APM power usage:

When the power setting is at FULL ON, all systems on the computer are running.

And, when the power setting is at APM ENABLED, unused devices can be shut down,
but the CPU and RAM are running on full power.

The APM STANDBY power setting stops the CPU, but retains programs in RAM and the
peripheral devices' configuration options.

The APM SUSPEND power setting either shuts down all PC components or switches them
to their lowest power settings.

Some computers hibernate by storing configuration information on the hard disk before
shutting the system down.

Although this method returns the system to its presuspension state more slowly than
APM STANDBY does, it is still quicker than restarting the system.

In APM SUSPEND mode, you can configure the BIOS using CMOS.

Most operating system settings are able to override CMOS settings, but all CMOSs
can initialize power management.

In many cases, you can use the CMOS to schedule wake-ups and standby and suspend
modes.

Some CMOSs can also track the system events that take place in APM modes and they
can monitor a device, such as a modem.

In Windows 98, you can use the Display icon in the Control Panel to access power
management functionality.

The Screen Saver tabbed page in the Display Properties dialog box provides energy saving features.

And you can set the power saving scheme to match your PC's power saving with its
particular circumstances.

You can also access this functionality through the Power Management icon in the
Control Panel.

You can schedule the interval that either the monitor or hard drive is to remain
on before switching itself off or going on standby.

Advanced Configuration and Power Interface (ACPI) is a power management specification developed by Intel, Microsoft, and Toshiba, which improves on the flexibility and
usefulness of APM.

While APM is a BIOS-based power management tool, ACPI is operating system based,
thus enabling intelligent control over power consumed by each device attached to
the computer.

For full ACPI functionality, both hardware and software need to be ACPI-compliant.