You may have wondered about the various settings that are contained in the BIOS of the machines you support. By changing some of these settings, you can improve the performance of the computer, resolve hardware conflicts, and prevent some problems from arising in the first place. This Daily Drill Down discusses basic BIOS options that are most likely to be useful to you in troubleshooting system problems and enhancing overall performance.
A BIOS bio
Every motherboard has a BIOS chip, which directs the input/output (I/O) operations of all the devices in or attached to the system. This includes communications between the processor and memory, L1 and L2 cache, as well as devices such as the keyboard, mouse, video display adapter, and disk drives. Every BIOS has its own features, characteristics, and idiosyncrasies, so this Daily Drill Down talks in generic terms about typical options that are found on the most popular BIOS chips on modern motherboards.
The best source of accurate, detailed information about the BIOS in your system is the manual that came with your motherboard. In case you don’t have a manual, most of them are readily available on the Web from the board’s manufacturer. That document will describe the various BIOS options and the functions served by each setting, along with some recommendations for the optimal choices for each.
Most generic motherboards today use BIOS components from Award or American Megatrends, Inc. (AMI). Another long-time BIOS provider, Phoenix, has merged with Award, and new BIOSs from the merged company will carry the Phoenix name. Some large computer manufacturers have their own BIOS chips, which typically offer you far fewer options than are found on Award or AMI BIOSs.
On a typical Award/Phoenix BIOS, when you enter the Setup routine, you are presented with a menu of some 10 to 14 choices. We will explore these options in the following sections:
- Standard CMOS setup
- BIOS features setup
- Chipset features setup
The next Daily Drill Down in this series will cover these options:
- Power management setup
- Integrated peripherals
- PNP/PCI configuration
- Load setup defaults
- Password settings (User, Supervisor, Power On)
Just a note of caution—even different versions of a BIOS from the same manufacturer may have different options, and in some cases they may appear on different screens. If you don’t see a particular feature or option on the screen described here, look around on other screens and see if the BIOS provider has chosen a different place to put it.
One time you will surely need to venture into your BIOS is after your CMOS battery has expired and the BIOS no longer knows anything about the configuration of the machine. When that happens, you will be greeted by a message at power-on time that says, “CMOS information not found,” “Must run setup,” or words to that effect. If that situation arises, you need to perform three steps, in this sequence, from the CMOS Setup menu:
- Load Setup Defaults
- Standard CMOS Setup
- IDE HDD Auto Detection
You’ll save yourself a lot of trouble if you keep a record of your system configuration, known as a hardware inventory, on hand for just such an emergency. Go into your BIOS and your operating system and record critical information about your system. See the Daily Drill Down “Preparing a system and driver inventory of Windows NT” for tips that apply to any system.
1. Load Setup Defaults
This step loads “safe” settings for all of the BIOS features that are required for the system to be functional. You may want to optimize some of these settings later, but this is a reasonable starting point for a wide range of BIOS settings.
2. Standard CMOS Setup
On this screen, there are only a few settings to make and they’re pretty straightforward. This is where you will enter the date and time, specify the floppy drives installed in the system, and select the video adapter, which should be set to EGA/VGA. You also have the option to specify on which error conditions to halt the system; this will usually be set to Halt On All Errors. It is possible to enter your hard drive parameters on this screen, but that information is more safely entered using the HDD Auto Detection screen, covered below.
3. IDE HDD Auto Detection
This screen is used to automatically detect any IDE hard disk drives attached to this motherboard. When you choose this menu selection, the BIOS queries the primary IDE controller to determine what type of hard drive is connected as the master device. The result of this query (if a hard drive is attached) will be a description of the drive characteristics, starting with the drive size in megabytes and ending with the mode in which to access the drive.
You will sometimes be given a list of two or three drives at this point, all having the same or nearly the same size, but the rest of the specifications will vary considerably. This ambiguity is most common for hard drives of 528 MB or higher capacity. For such a drive, you may need to choose the appropriate one from the list of drives. In most cases, the choice that shows a mode of LBA will be the appropriate selection for a Windows 95 or 98 machine.
LBA stands for Logical Block Addressing, and it is usually the preferred method of drive translation settings for Windows 95 or 98. If this computer is running a different operating system, you may need to choose Normal or Large in order for the drive to function correctly in that environment. In any event, if the hard drive is not recognized properly using the selection you’ve made, you simply need to come back into this screen and choose a different configuration until you find the right one.
Following detection of the primary master hard drive, the BIOS will search for a primary slave hard drive, then a secondary master and secondary slave. If you only have a single hard drive installed on this system, you may skip detection of the subsequent drives (usually by hitting the [Esc] key) and return to the CMOS Setup menu.
Once the hard drives have been set up through this screen, they will appear in the Standard CMOS Setup screen as well. Note that other IDE devices, such as CD-ROMs and Zip drives, will not be detected by IDE HDD Auto Detection (that’s for hard disk drives only), but they may appear on the Standard CMOS Setup screen.
Other BIOS features
The settings on this screen allow you to prevent some problems, troubleshoot and fix others, and possibly enhance the performance of the system. Here are the parameters you may want to change:
Although this sounds like a logical feature to enable, in your normal operating environment it is likely to set off a lot of false alarms; consequently, it is best to leave it disabled and use antivirus software with current virus signatures to detect actual virus activity.
CPU internal cache and external cache
There may be rare instances of troubleshooting when you suspect that a problem is caused by the cache memory in the system, either Level 1 (internal) or Level 2 (external). To isolate either of these as possible sources of the problem, you may disable them using these settings. L1 and L2 cache greatly improve system performance, so be sure both are enabled after you have eliminated them as the source of the problem.
This setting tells the BIOS where to find the boot record. The boot record contains the instructions that load the operating system, whether it’s MS-DOS, Windows 95/98, NT, 2000, or any other OS. This option specifies the devices to be examined for the boot record and the sequence in which they are to be searched.
Most systems come with the default set to A, then C. This means that if a bootable floppy disk is in the A: drive, the boot record on that floppy disk will be used; if there is no disk in the A: drive, the system looks next to the C: drive for a boot record and, if one is found, boots from that hard drive.
Some newer systems offer the ability to boot from a Zip drive, LS-120, or a CD-ROM. You may also have an option for a SCSI hard drive or a Boot PROM from a network interface card. You need to determine the most appropriate boot sequence for the computers you are maintaining, but here are some considerations on the subject.
If you stick with the default setting (A, C), any user can boot from any bootable floppy disk. You may not want this to happen, as a bootable floppy could contain illegal software or viruses. Changing the boot sequence to C, A means the computer would attempt to boot from the floppy drive only if no hard drive were found. Otherwise, inserting a bootable floppy in the A: drive would have no effect.
On the other hand, if you need to boot from a floppy disk to run diagnostics or bring a machine to life that is unable to boot from the hard drive, you may need to change this setting back to A, C until the problem with the hard drive is resolved.
Another possible vulnerability with this setting involves new computers from large computer manufacturers that provide a restore CD with the system. These machines are typically set to boot from the CD-ROM first, then A, then C. The potential problem with this setting is that if the restore CD is inadvertently left in the drive and the machine is restarted, the Restore procedure will be initiated and potentially reformat and overwrite the hard drive to its original contents.
Although this is an unlikely scenario—and would probably require several affirmative keyboard responses to play out—a safer approach would be to remove the CD-ROM from the boot sequence and enable it only when it is really required.
This section of the setup routine allows the system to copy the BIOS code from ROM into the system RAM, which is much faster memory. Since ROM typically has a speed of some 150ns, and RAM on a Pentium II or later system may be as fast as 7ns, this technique can result in a great performance improvement in BIOS operations. There are two reasons you may not want to change these settings from the default, though.
The first potential problem involves the area of RAM that is used for shadowing. The range of memory that may be used is the area above the first 640 KB of RAM to the end of the first megabyte. Unfortunately, this same area may be used by various adapter cards and integrated peripherals in your system; thus, you have the possibility of a memory conflict between the shadowed BIOS and I/O devices.
You can avoid this problem by shadowing only specific areas of RAM. This BIOS shadowing screen offers you six discrete 16-KB ranges in which to enable or disable shadowing. If you enable one of these areas at a time, save the settings, exit, and then bring up your normal operating environment, you can see whether that specific area conflicts with any devices installed in that system. In making this determination, be sure to use all of the I/O devices, including your network interface card, sound card, USB devices, and CD-ROM.
If the range you have enabled causes no conflicts, you can then go back into the BIOS and enable another range and then repeat the process as many times as necessary. On a modern PC with a typical range of I/O devices installed, you’re likely to have conflicts in at least one range on this list.
You may note that the video BIOS shadow is enabled by default, which seems counterintuitive. After all, every system has a video display adapter, so how can you safely shadow the BIOS into that area? The answer is that this range refers to the memory used by the original monochrome display adapter and color/graphics adapter on the original PCs, XTs, and ATs. The video graphics array (VGA) adapter used in modern systems uses a different memory range, so there is no conflict in shadowing into the video BIOS area.
Now, having been through all of that, the other reason you may not want to use BIOS shadowing is that it may have little effect on the performance of your system. If you are running a 32-bit operating system, such as Windows 95/98, NT, or 2000, those operating systems load 32-bit drivers into RAM at startup. Instead of using the 16-bit, slow ROM code while running, they already execute from RAM; the ROM is used only during system startup.
On the other hand, for machines that are still running 16-bit operating systems, such as MS-DOS and/or Windows 3.x, you definitely will want to experiment with BIOS shadowing for improved performance. Especially for a fast, new machine running legacy DOS and Windows 3.x applications, this feature can be worthwhile to implement.
Chipset features setup
The settings on this screen are mostly related to the memory installed in your system. You normally won’t need to change any of the default settings here, but I will cover a few possible exceptions.
CPU host/PCI clock
If your BIOS offers you this option, it is allowing you to specify how the front-side bus, or FSB, speed is determined. You will usually want to leave this set to Default, which interrogates the CPU and sets the FSB clock automatically to 66 MHz or 100 MHz, depending on the processor speed.
If you choose to manually set the FSB clock to 100 MHz, you could seriously jeopardize the reliability and stability of the system and potentially damage the processor and other components if they’re not rated for this speed. If you have 100-MHz-capable components and want to be sure that the FSB speed is set correctly, there’s no harm in choosing 100 MHz instead of the default setting.
Memory speeds and types
The next group of settings on this screen allows you to change the specifications of the memory that is installed in the system. If you replace the existing memory with faster SIMMs or DIMMs, you’ll need to tell the BIOS about it so that the memory-refresh circuitry will perform properly.
Similarly, if you upgrade your FPM memory to EDO or SDRAM, you’ll need to make the BIOS aware of the type of memory that is installed so that it can be handled properly. Some motherboards allow you to specify different memory types in different banks, but the safest approach is to use the same level of memory technology in every slot.
This screen may also give you the ability to monitor the system for overheating conditions, which may be detected directly or indirectly. The newest cases and motherboards monitor the actual temperature inside the case, and on these systems, the BIOS can sound an alarm when a specified temperature is reached. The actual CPU temperature may be monitored as well.
Alternatively, your BIOS may give you the option to set off an alarm if the CPU cooling fan quits working or drops below a specified RPM range. Note that this feature is available only if the CPU fan is connected to the motherboard, where it can be monitored; if your CPU fan is connected directly to the power supply, these settings will not apply.
Whatever overheating alarms your BIOS offers, enable those that will legitimately call your attention to an overheating situation. If your system does actually overheat, you’ll want to know about it as soon as possible, before any permanent damage is done.
The BIOS available in a generic computer presents many options for fine-tuning your operating system. A significant number of these options may not be available in proprietary systems made by large computer manufacturers. To be sure of the best settings, consult your motherboard documentation or the BIOS manuals easily found on the Web. In this Daily Drill Down, I’ve presented an overview of CMOS settings, BIOS features, and chipset settings. In my next Daily Drill Down on this topic, I’ll cover power management, peripherals, and other useful BIOS settings.
The authors and editors have taken care in preparation of the content contained herein but make no expressed or implied warranty of any kind and assume no responsibility for errors or omissions. No liability is assumed for any damages. Always have a verified backup before making any changes.