The BIOS (Basic Input Output System) is often dismissed as being simply the glue that holds your hardware together, little more than a pot of your most basic settings. However, while an OS is far more configurable, the BIOS holds more than its fair share of handy tweaks, many of which can provide considerable performance gains. The average PC user generally feels no need to tweak the BIOS, but a power user knows that it holds plenty of important settings that can provide additional functions, or improve performance. The only costs involved are the time it takes to affect them.

BIOSes vary greatly depending on not just the BIOS manufacturer but also the motherboard manufacturer. This combined effect makes it difficult to provide definitive instructions. Menus differ and the terms used to describe settings often change. That said, you’ll still find more similarities than differences between BIOSes. Functions may have different labels, but the end results will be similar. For the purposes of this feature, we’ve opted to use the Award BIOS as our main demonstration example, although the AMI and Phoenix counterparts offer similar functions. Even different versions of Award vary, so you need to exercise a little common sense when following instructions. Regardless of all these caveats, and no matter which BIOS you have, the following advice will help you make the most of it.

Setup
To get started, you’ll need to enter the BIOS set-up utility. You do this by pressing a key or combination of keys as you start your PC. For most BIOSes this is just the delete key [del], but watch for indications of alternative keys during boot. You can normally see the keys that you need to press on the initial screens of the boot process. If you miss it, just press the reset button and try again.

Once in the BIOS set up utility, you may be forgiven for thinking that you’ve stepped back in time. Few BIOS utilities support mouse control, so you navigate using the keyboard’s arrow keys, pressing [Enter] to select an option. Some BIOSes use [Pg Up] and [Pg Down] to change options, but you’ll find a summary of the control keys on this screen. [Esc] usually moves you back up one level, or quits without saving changes if you’re already at the main BIOS set up screen. [F10] enables you to quit, saving the changes you’ve made.

With the correct tweaks to your BIOS, you can achieve significant performance gains. Sometimes this is achieved by overclocking, but some performance gains can be made just by ensuring that the most appropriate settings are chosen. BIOSes aren’t normally optimised when shipped, so you can make gains by confirming that your BIOS is correctly set for your components.

Many motherboards have an overall option to increase speed. Some offer settings like Normal, Fast and Turbo. You may also find a setting like Load Optimized Defaults in some BIOSes. These will improve performance, but they won’t get the best out of your system. Only by understanding the capabilities of each piece of hardware in your PC and then making appropriate alterations in the BIOS can you truly push your system to the max.

CPU frequency
You’ll find the ability to change CPU speed or frequency, or the Front Side Bus, in most BIOSes. This may be called CPU Host/PCI Clock. The clock speed will be considerably slower than that of the processor itself, being somewhere between 66MHz and 133MHz. Increasing this by small increments is the most common method used to overclock a processor. Resist the temptation to increase it by larger steps as this is where damage often occurs. This is normally located in a section called Frequency/Voltage Control, although some BIOSes have separate sections for the processor. Once you’ve attempted an overclock, head to the PC Health section of the BIOS. This will give you a reading of the CPU temperature. Try to keep it below 40 degrees Celsius. If it has risen above this, go back and undo your tweak.

Memory matters
To optimise your RAM performance, open the Chipset Features section of the set up utility and tweak the Memory Timings options. If the memory slots in your motherboard use identical memory sticks, or you have just one installed, choose By SPD. Otherwise, find out the capabilities of your memory with a benchmarking program like SiSoft Sandra Max3 and set the timing accordingly. Make sure that the DRAM clock setting matches your setting for memory timings.

CAS Latency (Column Access Select Latency) is a measure of how quickly data can be read from memory. This is measured in clock cycles and its value is normally 3. However, some faster memory has a CAS latency of 2. It’s worth trying out setting the CAS latency time to 2 to see if this improves performance, but be prepared to switch it back again if instabilities arise.

AGP slot
While your motherboard and graphics card may both support AGP 4x or 8x, performance will suffer if the AGP mode in the BIOS is set to a lower value. Ensure this setting matches the maximum your hardware can handle. The AGP aperture size is the amount of system RAM allocated to the AGP for video purposes. You can set this to up to half of your system RAM.

Some BIOSes permit you to enable AGP Fast Write Transaction. This works on AGP slots that support 4x and 8x, allowing data to be sent directly from the chipset to the graphics card without making a copy in system memory for the graphics card to fetch. AGP sideband addressing permits some cards to request data at the same time as receiving it. This improves performance but can produce instabilities with some graphics cards.

In newer systems, disable system BIOS, video BIOS and Video RAM Cacheable are all settings that copy data into the L2 cache. This would improve performance if Windows used this feature. With them disabled, you preserve the L2 cache for other use. Equally, if you don’t play graphic-intensive games from DOS, you can disable Video BIOS Shadowing and Video BIOS Cacheable because recent versions of Windows (2000, XP and above) don’t take advantage of these features.

Better boots
More often than not, hard drives are automatically detected. However, you can save some boot time by setting the IDE drives to User and then manually specifying the drive parameters. These can seem a bit complex and daunting, but you can find most of them printed on the drive itself. Some BIOSes have a separate Detect IDE utility that you can use to retrieve the relevant information. Some older BIOSes don’t automatically detect hard drives and therefore require you to enter the specifications manually anyway.

Here’s a quick guide to hard drive specifications used in the BIOS. Size is generally a measure of the number of heads, sectors and cylinders. You should find the number of cylinders printed on the hard drive label, and the same goes for the number of heads. Write Precompensation will be determined automatically so don’t worry about it. Ignore Landing Zone or set it to zero. It’s used for older drives that don’t ‘auto-park’ their heads, but all modern hard drives have it. Sector indicates the number of sectors per track. If this isn’t indicated on your drive, try 17 and 26, which are common settings.

You can save time when booting your PC by enabling Quick Boot or the Quick Power On Self Test. You’ll find this in the Advanced BIOS features. With today’s huge RAM sizes, any test that involves a RAM count takes ages. If necessary, you may need to disable the RAM test separately. It’s also worth turning off the Boot Virus Detection, as this should have been covered by the use of an up-to-date virus checker.

The boot sequence determines the device that’s first used to start up your PC. A common sequence starts by interrogating the floppy drive, then the CD drive and finally the first hard disk. You can speed up this process by setting the primary hard drive as the first boot device, thus bypassing checking the floppy and CD drive for boot records. However, it’s useful to boot from floppy or CD at times, but you can edit the BIOS to enable booting from these. Note that modern BIOSes can enable booting from USB or FireWire devices, as well as Zip and LS120 drives. You can speed up the process by setting unwanted boot devices to None.

Peripherals and ports
There’s more to BIOS tweaking than just improving performance, although a speedy PC is usually a happy one. Management of your peripherals, including your serial, parallel and USB ports, provides you with greater control over your hardware. The Integrated Peripherals section gives you access to a number of changes that you can make to your ports. If you use a parallel port scanner and run a printer from this port, you’ll want to ensure that it’s bi-directional. There are four options for the parallel port. The first is Normal or SPP.

This is bidirectional but very slow. ECP (Extended Capabilities Port) works well for devices that transfer lots of data. EPP (Enhanced Parallel Port) is better for devices that switch data direction a lot. Some offer a mode called EPP + ECP. This offers the best of both worlds, although it takes up two IRQ (interrupt requests) and this may be significant if you have a lot of devices permanently hooked up. You may find a setting named ‘ECP mode use DMA’. This controls the DMA (Direct Memory Access) channel used for ECP transfers. It’s 3 by default, but you can change it to 1 in case of a conflict.

Enable or disable the serial ports using the Onboard Serial Port settings. The defaults set IRQ 4 with 3F8 (a reference to a memory address in the lower portion of the memory map) to COM 1 and IRQ 3 with 2F8 for COM 2. If you disable either of these, you free up the IRQ that’s associated with it.

Also often included in the Integrated Peripherals section is the USB controller, where you can enable or disable your motherboard’s onboard USB controller. You may also find USB keyboard and mouse settings here. While Windows will probably handle these, you may want to ensure that USB keyboard is enabled if you want to use it in DOS or in the BIOS set up utility.

The Onboard IR Function setting is for enabling IR devices connected to the motherboard. Use the setting indicated in the documentation for your infrared device. You may find duplex settings for the IR port here, so you can choose between full and half duplex transfer modes.

Power management
Power management features may hit performance but they save energy and help safeguard the future of the planet. Most involve shutting down parts of your system after a certain amount of idle time. There are several power-saving states that a PC can enter. Dozing slows the processor down to around half normal speed. Standby shuts down the hard drives and graphics output. Suspend closes down all devices except the CPU. Inactive shuts down the processor and powers down the L2 cache. HDD power down shuts down the hard drive. Change the PM Timers to set the waiting period before the PC powers down its hard drives or goes into Suspend or Doze mode.

Choose Power Management from the main BIOS set up menu. If you have a Global Power Management setting, set it to Enabled. Other settings enable you to specify what components power down when the system is idle. Select the Power On Function to specify what action will restore power. You can assign this to a hotkey or password, or opt to restore power when any key is pressed. You can also set your PC to wake up at a specified time on receipt of a signal from an attached device or from the local network. Enable Wake on LAN or WakeUp by PME# of PCI to set these up.

PC Health
After all your fiddling, you should find that your PC boots up faster and is less wasteful of resources. However, this only required changes from generic settings to those more specific to your system, and will subsequently have had only a minor effect on your overall system performance. Tweaks to clock and timings will have had the greatest effect, but be sure to check your PC’s healthy before you assume all is well. This is exactly what the PC Health section of your BIOS enables you to do.

CPU and system temperatures as well as fan speeds can be found here, which is the best way to check if a tweak takes the temperature too high. You can also set levels at which the BIOS can take action to preserve its components. CPU Warning Temperature enables you to set a level at which you’re warned when things are getting too hot, and CPU Shutdown Temperature allows the BIOS to shut the processor down should you not take heed of the previous warning. It’s better to be safe than sorry.