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Not all device drivers are found in the CONFIG.SYS file. Advanced operating
systems use .INI files to set up and start devices.
Device drivers can access the hardware in five ways.
v Operating system direct to hardware using a direct driver
Direct drivers, which bypass BIOS, have the advantage of faster throughput, but
the disadvantage of limited error-handling capability and reduced software and
hardware compatibility and flexibility. This method is not used in the IBM PC
Series systems.
v Operating system to BIOS to hardware
This is the recommended way. It’s the most flexible because it is independent of
the hardware.
v Applications to operating system to BIOS to hardware
This method is inflexible and is dependent on the operating system.
v Applications to BIOS to hardware
This method has some flexibility but it is dependent on the BIOS.
v Applications to hardware
This method is dependent on the hardware and is very inflexible. However, it is
very fast, very efficient, and it has no overhead.
Hardware considerations
Use the following tools to help identify and resolve hardware-related problems.
v Power-on self-test (POST)
v POST Beep codes
v Test programs
v Error messages
POST does the following operations.
v Checks some basic system board operations
v Checks the memory operation
v Starts the video operation
v Verifies that the diskette drive is working
v Verifies that the hard disk drive is working
Use the test programs that come with this HMM or with the system you are
servicing to test the IBM components of the system and some external devices.
Also, from the DOS prompt or from OS/2 Utilities, use the CHKDSK command to
check and repair hard disk data allocation errors.
Error messages generated by the software (the operating system or application
programs), generally are text messages. However, error messages can be text,
numeric, or both text and numeric.
Any time there is an error message indicating a problem with the system, follow
the General Checkout procedures in this HMM to resolve the problem.
Basically, there are five types of error messages.
v POST error messages are displayed when the POST finds problems with the
hardware or detects a change in the hardware configuration.
Chapter 10. Related Service Information 131