Upgrading and Repairing PCs

Disassembly/Upgrading Preparation

After you've built your system, you probably will have to open it again sometime to perform a repair or an upgrade. Before you power off the system for the last time and begin to open the case, you should learn and record several things about your computer. Often, when working on a system, you intentionally or accidentally wipe out the CMOS Setup information. Most systems use a special battery-powered CMOS clock and a data chip that is used to store the system's configuration information. If the battery is disconnected, or if certain pins are accidentally shorted, you can discharge the CMOS memory and lose the setup. The CMOS memory in most systems is used to store simple things such as how many and what type of floppy drives are connected, how much memory is in the system, and the date and time.

A critical piece of information is the hard disk–type settings. Most modern BIOS have an autodetect feature that reads the type information directly from the drive. I recommend you set the drive type to Auto, which automatically sets all the necessary parameters for you. With older BIOS you must explicitly tell the system the parameters of the attached hard disk. Therefore, you need to know the current settings for cylinders, heads, and sectors per track.

If you do not enter the correct hard disk–type information in the CMOS Setup program, you will not be able to access the data on the hard disk. I know of several people who lost some or all of their data because they did not enter the correct type information when they reconfigured their systems. If this information is incorrect, the usual results are a missing operating system error message when the system starts and the inability to access the C: drive.

Some people think that it's possible to figure out the parameters by looking up the particular hard disk in a table. (I have included a table of popular hard disk drive parameters in the Technical Reference on the DVD-ROM. This table has proven to be useful to me time and time again.) Unfortunately, this method works only if the person who set up the system originally entered the correct parameters. I have encountered a large number of systems in which the hard disk parameters were not entered correctly; the only way to regain access to the data is to determine, and then use, the same incorrect parameters that were used originally. As you can see, no matter what, you should record the hard disk information from your setup program.

Most systems have the setup program built right into the ROM BIOS software. These built-in setup programs are activated by a key sequence usually entered during the POST. Most systems show a prompt on the screen during the POST indicating which key to press to enter the BIOS Setup.

The major vendors have standardized on these following keystrokes to enter the BIOS Setup:

• AMI BIOS. Press Del during POST.

• Phoenix BIOS. Press F2 during POST.

• Award BIOS. Press Del or Ctrl+Alt+Esc during POST.

• Microid Research BIOS. Press Esc during POST.

If your system does not respond to one of these common keystroke settings, you might have to contact the manufacturer or read the system documentation to find the correct keystrokes to enter setup.

Some unique ones I have encountered are as follows:

• IBM Aptiva/Valuepoint. Press F1 during POST.

• Older Phoenix BIOS. Boot to a safe mode DOS command prompt, and then press Ctrl+Alt+Esc or Ctrl+Alt+S.

• Compaq. Press F10 during POST.

After you're in the BIOS Setup main screen, you'll usually find a main menu allowing access to other menus and submenus offering various sections or screens. When you get the setup program running, record all the settings. The easiest way to do this is to print it. If a printer is connected, press Shift+Print Screen; a copy of the screen display will be sent to the printer. Some setup programs have several pages of information, so you should record the information on each page.

Many setup programs allow for specialized control of the particular chipset used in the motherboard. These complicated settings can take up to several screens of information—all should be recorded. Most systems return these settings to a BIOS default if the CMOS battery is removed, and you lose any customized settings you might have changed. See Chapter 5 for more information on the BIOS settings.