Specifications

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How Startup BIOS Controls the Boot Process
3
The switch on the rear of the case simply turns off the power abruptly and is a “hard”
power button. If you use this switch, wait 30 seconds before you press the power
button on the front of the case to boot the system. This method gives you the greatest
assurance that memory will clear. However, if Windows is abruptly stopped, it might
give an error message when you reboot.
How the front two buttons work can be controlled in BIOS setup. Know, however, that
different cases offer different options.
Soft power button
does a normal
Windows shutdown
Hard power button
abruptly reboots
Hard power switch
on rear of case
Figure 3-33 This computer case has two power buttons on the front and one power switch on the rear of the case
Courtesy: Course Technology/Cengage Learning
A+ 220-701
A+
220-701
1.2
3.4
THE STARTUP BIOS CONTROLS THE BEGINNING OF THE BOOT
The startup BIOS is programming contained on the firmware chip on the motherboard that is
responsible for getting a system up and going, and finding an OS to load. A successful boot
depends on the hardware, the BIOS, and the operating system
all performing without errors. If errors occur, they might stall
or lock up the boot. Errors are communicated as beeps, as text
messages on-screen, or as recorded voice messages.
The functions performed during the boot can be divided into four parts, as shown in the fol-
lowing list. The first two items in the list are covered in detail in this section. (The last two steps
depend on the OS being used and are covered in later chapters.)
1. The startup BIOS runs the POST and assigns system resources. Recall from Chapter 2
that the POST (power-on self test) is a series of tests performed by the startup BIOS to
determine if it can communicate correctly with essential hardware components required
for a successful boot. The startup BIOS surveys hardware resources and needs, and
assigns system resources to meet those needs (see Figure 3-34). The startup BIOS begins
the startup process by reading configuration information stored primarily in CMOS
RAM, and then comparing that information to the hardware—the processor, video slot,
PCI slots, hard drive, and so on. (Recall that CMOS RAM is a small amount of mem-
ory on the motherboard that holds information about installed hardware.)
2. The startup BIOS program searches for and loads an OS. Most often the OS is loaded
from drive C: on the hard drive. The boot sequence information stored in CMOS
RAM tells startup BIOS where to look for the OS. Most BIOSs support loading the
OS from the hard drive, a floppy disk, a CD, a DVD, or a USB device. The BIOS turns
to the specified device, reads the beginning files of the OS, copies them into memory,
and then turns control over to the OS. This part of the loading process works the
same for any operating system; only the OS files being loaded change.
Beep Codes
Video
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