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CMOS memory settings – what to do if the battery goes flat So you’ve just bought a new computer? Would you know what to do if the backup battery on the motherboard went flat & the computer lost its vital settings? Here’s how to get things going again. By GREG SWAIN They used to say that there were two certainties in life: death and taxes. To that, you can now add a third. Yep, you’ve guessed it – computer failure. If the floppy drives don’t get you first, then eventually the hard drive will. Or perhaps the monitor will croak (a common fault), or the hard disc controller card will go haywire and scramble your files. Or maybe the contacts on the video con­troller card will get dirty and the machine will spit out confus­ing RAM parity error messages. And then there’s a flat battery on the motherboard. This one’s virtually guaranteed to happen at some stage, often after just 2-3 years from new. When that happens, your machine loses vital setup information that’s stored in a CMOS memory on the motherboard and refuses to boot up. The type of backup battery used varies but generally a lithium battery or a rechargeable nicad battery is used. In theory, a nicad battery is “topped up” while the computer is switched on but, regardless of the type used, they don’t last for ever. Indeed, a rechargeable battery can soon go flat if the computer is not used very much or has not been used for some time. If the existence of this backup battery comes as a surprise to you, then you’re not alone. Very few retailers (if any) point this out when the machine is purchased. Not that there’s any deliberate conspiracy involved. After all, there are far more important things to talk about in the store – things like software, printers, CD-ROMs, hard disc size, how much RAM, what size monitor and, of course, how much it’s all going to cost. The backup battery on the mother­ board is a mere detail! And so you take your new computer home. And you plug it in and everything is fine for a few years. And then, one day, the machine refuses to boot up after performing its memory check routine. What gets lost? The CMOS setup program is usually accessed by hitting the <DEL> key after the system has completed its RAM-checking routine during boot-up. The CMOS setting can then be inspected by selecting “Standard CMOS Setup” from the menu & pressing the <ENTER> key. 4  Silicon Chip What is this vital information that the computer loses? Well, when you turn your computer on, the system needs to be told certain things in order to boot up successfully. This information mainly concerns the amount of RAM, the disc drives and the type of video controller used. For example, the system needs to know what type of floppy disc drives are installed, along with the hard disc type and its physical parameters. These parameters include the number of cylinders, heads and sectors on the hard disc. When the computer is initially set up, this information is entered into a setup program and stored in the CMOS memory. Unfortunately, CMOS memory is screen similar to that shown in Fig.2. As indicated by the legend at the bottom of the screen, you can select any of the entries using the arrow keys and you can modify these entries using the Page Up and Page Down keys. Do not alter any of the entries since they will be correct for your computer. Instead, make a note of all the settings on a piece of paper, with particular emphasis of the hard disc drive parameters, and store this in a safe place. Alternatively, you can obtain a printed copy by pressing the <Print Screen> key. Note, however, that only the standard ASCII characters will print correctly using this method. Any graphics will either be omitted or will print as special characters. When you have made your copy, hit <ESC> to exit this screen, then select “Do Fig.2: this is the Standard CMOS Setup screen. Make a record of all the settings for your Not Write To CMOS & Exit”. computer (they will generally be quite different from those shown here), with particular Setup will then ask you if emphasis on the hard disc drive parameters. Alternatively, you can hit the <Print Screen> you want to quit without key to obtain a printed record. saving. Type <Y> to answer yes, then press <enter> to volatile which means that it loses will be self-evident (eg, the date, the exit the setup program. Your comdata if power is removed. Normally, types of floppy disc drives used and puter will now continue to boot up the backup battery maintains the the primary display), the hard disc as normal. CMOS settings when the computer type and the number of cylinders, Another (even easier) way of obis switch­ed off but when the battery heads and sectors on the disc will be taining the hard disc drive parameters fails, these settings are lost. And when a mystery. is to use the Microsoft Diagnostics that happens, the computer no longer If you have a manual on the hard program (MSD.EXE) that comes with knows how to access the drives or the disc, then it’s a simple matter of look- MS-DOS 6.0 and above. First, quit video card. ing the data up in there. If you don’t Windows and go to the C:\> prompt; At this stage, most users simply have a manual, you can quite easily ie, type cd \ <enter>. Now type MSD assume that their computer has de- check the current CMOS settings. <enter>. A screen similar to that veloped a fault and pay to have it ser- The following procedure is typical of shown in Fig.3 will now appear. If viced. But what if you need to get the most computers, although you may you now select the “Disc Drives” computer going immediately, or you’re encounter some variations along the button, the program will check your poor and cannot afford the service fee? way. Be sure to consult the manual system and display a screen similar Well, there’s good news and there’s for your motherboard, to obtain the to that of Fig.4. good news. You can get the computer exact procedure. As before, make a note of all the disc going immediately and a permanent First, switch the computer on and parameters (or hit <Print Screen>) and fix will cost you no more than half an wait until it has com­pleted the RAM store it in a safe place. This done, click hour of your time and a new battery. checking procedure. The setup pro- OK to go back to the main menu, then Let’s see how we go about restoring gram, which is contained in ROM press <F3> to exit MSD. the system. (read-only memory), is then (usually) entered by pressing the <Del> key. Restoring the settings Be prepared Most systems then display a warning Armed with all this information, it’s The fix really starts back when you screen, after which you press any key now easy to restore the CMOS settings first purchased your computer. One (other than <Esc>) to obtain a screen when the power fails. All you have to of the first things that you should do similar to that shown in Fig.1. do is enter the Standard CMOS Setup Selecting “Standard CMOS Setup” Program (just hit <DEL> after the is make a record of the existing CMOS setup. While most of the data re­quired and pressing <enter> now gives a computer completes its memory check May 1995  5 “yes” to the question “Save CMOS Settings & Exit?” and the job is done. Your computer will now complete its boot-up procedure. Lost records Fig.3: the Microsoft Diagnostics (MSD) program is accessed by first quitting Windows, then going to the C:\> prompt & typing MSD. This is what the opening screen looks like. By clicking on the buttons, you can check out the various operating parameters of your system. What if you didn’t make a record of your CMOS settings or you’ve lost the bit of paper with all the disc drive parameters? There’s a way around that as well, since all the relevant parame­ ters are usually printed on a label that’s attached to the drive unit. The problem here is that the hard disc drive is usually buried in the drive bay beneath one or more floppy disc drives and perhaps a CD-ROM drive as well, which means that the label is obscured. The answer is to temporarily remove the hard disc drive so that the label can be seen. In some cases, this will be an easy job while in others it will be complicated by the need to remove the floppy disc drives first. Do not attempt this unless you know exactly what you are doing and always double-check that you have disconnected the power first (pull the plug from the wall). So the procedure for restoring the CMOS settings can be difficult or straightforward. It just depends on whether or not you made a proper record of the settings (and stored it in a safe place) when you first bought the computer. Replacing the battery Fig.4: to check the disc drive parameters, simply click the “Disk Drives . . .” button of the opening menu to obtain the screen shown above. This information can be printed out & stored for future reference (select “File”, “Print”). routine during boot-up) and re-enter the values. As explained above, the various entries are selected using the arrow keys, while the <Page Up> and <Page Down> keys are used to modify existing data. Hard disc types Be sure to select the correct type number for the hard disc drive before attempting to enter any of its other parameters. If the disc is a fixed type (ie, it has a type number between 01 and 46), then all you have to do is enter the type number. The re­maining parameters will then automatically appear. A type 47 disc, on the other hand, is a “User Defined” type. This means 6  Silicon Chip that you have to enter the various disc parameters (the number of cylinders, heads and sectors, etc) yourself. You do this by selecting the appropriate parameter and then entering its value directly via the keyboard. After entering the date and hard disc drive information, select the appropriate floppy disc drive, primary display and keyboard parameters. However, you don’t have to worry about the base memory and extended memory values, since the system checks these at switch-on and automatically displays the correct values. When all the entries are correct, press <Esc> to exit and select “Write To CMOS & Exit” from the menu – see Fig.1. Finally, press <Y> to answer While you can quickly get the computer going again, the re-entered CMOS values will be lost again when the computer is switched off. To affect a permanent cure, you must replace the battery before going through the CMOS setup routine. Once again, the exact procedure will depend on the mother­board. On some motherboards, the battery can be easily discon­nected and you can substitute an identical type obtained from a dealer. Be sure to disconnect the mains before opening up the case. The common practice these days is to use a 3.6V nicad bat­tery which is soldered directly to the motherboard. If you know exactly what you are doing, you can remove the motherboard from the case, de-solder the battery and substitute a new one. As well as the on-board battery, many motherboards also carry a 4-pin battery connector. This connector normally has a shorting jumper in- How To Create An Emergency System/Backup Disc Another thing that you should do when you first buy a com­puter (even before you inspect the CMOS settings) is create an emergency boot (or system) disc. This will enable you to boot the computer from one of the floppy disc drives if something goes wrong. A boot disc can be very useful under certain circumstances. For example, COMMAND.COM or the file allocation table (FAT) on the hard disc might become corrupted and the machine will refuse to boot. If this happens, you can boot the machine from your emergency system disc so that you can start troubleshooting. A clean boot disc is also handy if your machine “catches” a virus. By booting from a clean backup disc, you can prevent further damage from the virus and keep the virus out of memory while you run anti-virus software. A boot disc is created during floppy disc formatting by adding the “/s” switch to the format command. To do this, insert a floppy disc into drive A and type the following command at the c:\> prompt: format a: /s/u This will format the disc unconditionally and copy across three system files – IO.SYS, MSDOS.SYS and COMMAND.COM. Note that IO.SYS and MSDOS.SYS are hidden files, so you won’t see them in directory listings unless you include the “/a” switch with the “dir” command or instruct File Manager to show stalled between its two centre pins. If your motherboard has this connector (check the manual), an easy option is to purchase an external lithium battery that comes fitted with a matching 4-pin socket. This then plugs directly into the moth­erboard connector (remove the jumper first). It is also a good idea to remove the on-board battery, otherwise it may eventually leak and cause corrosion. You don’t have to remove the mother­ board to do this – just cut the leads to hidden/system files (click View, By File Type). Having created your system disc, it is also a good idea to back up two very important files in case you ever accidentally delete (or corrupt) them. These files are “autoexec.bat” and “config.sys” and they reside in the root directory of the hard disc. These two files are best copied to a sub-directory on your emergency system disc. To create a sub-directory, go to the C:\> prompt, insert the system disc into drive A, and log onto this drive by typing A: <enter>. Now, at the A:\> prompt, type md backup. This will create a subdirectory called “backup” on the floppy disc. Now type C: <enter> to go back the root directory on the hard disc. The two files can then be copied across by typing copy autoexec.bat a:\ backup <enter> and copy config. sys a:\backup <enter>. Alternatively, you can create a system disc and copy the autoexec.bat and config.sys files to a subdirectory on this disc using the Windows File Manager. To do this, first launch File Manager and choose Format Disk from the Disk menu. Choose the appropriate disc parameters (ie, the drive and disc capacity), then check the “Make System Disk” box and click OK. You can then create a sub­directory on the resulting system disc and copy the autoexec.bat and config.sys files into it by dragging them across from the C: drive. the battery using a pair of sidecutters. If necessary, remove some of the plugin cards on the mother­board to gain access to the battery. Finally, don’t be fooled by an onboard battery that meas­ures close to its rated voltage – ie, about 3.6V. A healthy battery will usually charge to about 4.2V. If the computer’s clock suddenly starts to lose by large amounts (eg, up to 20 minutes a day), then it’s a sure sign that the battery is on the SC way out. 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