The Boot Process
One area where people sometimes have problems with OS/2 is where the operating system fails to boot. To better determine where the problem lies we need to consider the various steps involved in actually booting up a computer running OS/2 from when we first press the power button until the workplace shell finishes loading. A knowledge of the steps that the computer goes through will assist you in determining where boot problems can occur and how you might deal with them.
Here is a list of the processes followed by a computer in booting to OS/2:
- You press the power button.
- The system powers up, the processor resets and starts the load sequence, the Power On Self Test (POST) is executed.
- Interrupt vectors are initialized and the Basic Input Output System (BIOS) is loaded.
- Depending on the BIOS settings the first floppy drive and/or CD ROM drive may be checked and if it contains a valid operating system in the boot sector then that operating system will be loaded and executed. Otherwise, the boot sector of the first hard drive (as identified in the BIOS) is found, loaded, and executed.
- If the boot partition contains OS/2 then the operating system is loaded, otherwise if the boot partition contains a boot manager then that is loaded and waits for you to select your operating system. Once you select OS/2 from the boot manager, the OS/2 operating system is loaded and executed.
- OS2KRNK and OS2LDR the kernel and loader modules are loaded.
- The system checks if you have pressed Alt+F1 or Alt+F2 to either bring up the recovery menu or turn on the driver load display mode.
- If the recovery screen is displayed then any option that you select there will be executed.
- The CONFIG.SYS file is loaded and its statements processed in the order BASEDEV, IFS, DEVICE, CALL, RUN, and finally SET. If driver load display mode is on then the drivers will be listed on the screen in turn as they are loaded. Note that the commands are executed in the order shown and not in the order that they are included in the config.sys file.
- The workplace shell starts up Presentation Manager and the interface changes from text based to graphics based.
- Finally, the desktop starts and the startup.cmd file is executed followed by the contents of the startup folder.
This article written by Stephen Chapman, Felgall Pty Ltd.