post and the boot process
DESCRIPTION
Booting Up Your Computer Refers to the computer bringing itself up to an operable state without user intervention Soft (warm) boot Uses OS to reboot Hard (cold) boot Uses on/off switch More stressful on the machine Copyright © Texas Education Agency, 2013. All rights reserved.TRANSCRIPT
POST and The Boot Process
Computer Technician POST and The Boot Process Copyright Texas
Education Agency, All rights reserved. Booting Up Your
Computer
Refers to the computer bringing itself up to an operable state
without user intervention Soft (warm) boot Uses OS to reboot Hard
(cold) boot Uses on/off switch More stressful on the machine
Copyright Texas Education Agency, All rights reserved. Overview of
Boot Process
Step 1: POST (Power-on self test) Step 2: ROM BIOS startup program
searches for and initializes an OS Step 3: OS configures the system
and completes its own loading Step 4: Load the Shell/GUI Startup
BIOS is in control for first step of the boot, then it turns over
control to the OS Copyright Texas Education Agency, All rights
reserved. Boot Step 1: POST Power-On-Self-Test
The first thing that the BIOS does when it boots the PC is to
perform what is called the Power-On Self-Test, or POST for short.
The POST is a built-in diagnostic program that checks your hardware
to ensure that everything is present and functioning properly,
before the BIOS begins the actual boot. It later continues with
additional tests (such as the memory test that you see printed on
the screen) as the boot process is proceeding. The POST runs very
quickly, and you will normally not even notice that it is
happening--unless it finds a problem. You may have encountered a PC
that, when turned on, made beeping sounds and then stopped without
booting up. That is the POST telling you something is wrong with
the machine. Copyright Texas Education Agency, All rights reserved.
Boot Step 1: POST Power-On-Self-Test
The speaker is used because this test happens so early on, that the
video isn't even activated yet! These beep patterns can be used to
diagnose many hardware problems with your PC. The exact patterns
depend on the maker of the BIOS; the most common are Award and AMI.
Some POST errors are considered "fatal" while others are not. A
fatal error means that it will halt the boot process immediately
(an example would be if no system memory at all is found). In fact,
most POST boot errors are fatal, since the POST is testing vital
system components. Copyright Texas Education Agency, All rights
reserved. Boot Step 1: POST Power-On-Self-Test
The first step of POST is the testing of the Power Supply to ensure
that it is turned on and that it releases its reset signal. CPU
must exit the reset status mode and thereafter be able to execute
instructions. BIOS checksum must be valid, meaning that it must be
readable. CMOS checksum must be valid, meaning that it must be
readable. CPU must be able to read all forms of memory such as the
memory controller, memory bus, and memory module. Copyright Texas
Education Agency, All rights reserved. Boot Step 1: POST
Power-On-Self-Test
The first 64KB of memory must be operational and have the
capability to be read and written to and from, and capable of
containing the POST code. I/O bus must be able to write / read from
the video subsystem and be able to read all video RAM. If the
computer does not pass any of the above tests your computer will
receive an irregular POST. An irregular POST is a beep code which
is different from the standard which can be either no beeps at all
or a combination of different beeps indicating what is causing the
computer not to past the POST. Copyright Texas Education Agency,
All rights reserved. Bios Screen example Copyright Texas Education
Agency, All rights reserved. Bios Screen example Copyright Texas
Education Agency, All rights reserved. Plug and Play (PnP)
Standard
Standard designed to make installation of hardware devices easier
Applies to OS, system BIOS, and hardware devices ESCD (extended
system configuration data) Plug and Play BIOS Copyright Texas
Education Agency, All rights reserved. Boot Step 2: Loading the
OS
Copyright Texas Education Agency, All rights reserved. Boot Step 2:
Loading the OS
A hard drive might contain more than one logical drive. The
partition table at the beginning of the drive contains information
about the location of each logical drive, indicates which drive is
the boot drive, and holds the Master Boot Record that begins the
boot process for the operation system. Copyright Texas Education
Agency, All rights reserved. Boot Step 2: Loading the OS
(DOS, 9x) Copyright Texas Education Agency, All rights reserved.
Boot Step 2: Loading the OS
Copyright Texas Education Agency, All rights reserved. Boot Step 3:
OS Initializes Itself
Operating system completes the boot process, DOS core is loaded.
Copyright Texas Education Agency, All rights reserved. Load the
Shell/GUI DOS Prompt
Boot Step 4: Load the Shell/GUI DOS Prompt Copyright Texas
Education Agency, All rights reserved.