The BIOS: An Introduction
The Basic Input-Output System (BIOS) is an essential set of routines in a PC, which is stored on a chip on the motherboard. It acts as an intermediary between a computer's hardware and its operating system. Without the BIOS, the PC's operating system would have no way to communicate with, or take control of, the hardware.
In other words, the BIOS is a crucial component of any computer. If its options are set incorrectly, the BIOS could slow your computer down by as much as 40%. Unfortunately, as new processors and motherboard chipsets are released, BIOS options continue to get even more confusing. As a result, many seasoned technicians are still baffled by the jargon-laced and confusing options available in a modern computer's BIOS setup program. Obviously, whatever motherboard you use will have differences from the model before it, but you can still get a feel from the common examples we will discuss in class for the sorts of adjustments that you can make.
Keep in mind that changing a PC's BIOS settings incorrectly can cause the PC to malfunction. If this happens, a BIOS reset will need to be performed to return to the default (read: unoptimized) "factory settings." This is usually activated by a jumper on the motherboard, which is easier said then done with many laptops!
Many large PC manufacturers such as Dell, HP, Gateway and Micron limit the options available to the end-user in the BIOS, in order to reduce ill-advised "tinkering" and the resulting support calls. As a result, you may not be able to take advantage of some of the advanced settings from these major vendors.
Most PCs briefly display a message describing how you can enter "setup," the program where BIOS settings are adjusted. You're allowed only a few moments to press the required key before your operating system starts to load. To enter your BIOS, turn on the PC and hold down, or press repeatedly, the key required to enter setup. On most PCs this is the DEL key, the F1 key or the F2 key
It is recommended that you reboot after each individual BIOS setting change to ensure that your system functions normally. If you make numerous changes before rebooting, and your system will no longer boot, you won't know which change is responsible for the failure.
Main Menu
Just below where you set the date and time you can define the specifics of your hard drives and other storage devices installed in the PC. Each time the PC boots, it most likely has to auto-detect and determine what storage devices are installed on the system. While this takes only a second or two on most systems, if you define these specifics rather than use auto-detection, your boot-up will be that much quicker.
To do this, simply select the drive, usually by highlighting it and pressing Enter. Then write down the numbers currently displayed for the Cylinders, Heads, Sectors, and LBA. On some BIOSes, you'll also have options for Block Mode as well as 32-Bit Transfer Mode. Change the drive type from AUTO to USER. Then key those numbers and options in exactly as they were displayed. On most modern computers, you will want LBA Mode, Block Mode, and 32-bit Transfer Mode all turned ON for your hard disk drive, even if they weren't before.
If there is no device attached to any one of the four possible drive location combinations, select NONE. For example, if you have one hard drive configured as a Primary Master and one CD-RW configured as a Secondary Master, be sure to set both the Primary and Secondary Slave options to NONE. If you leave the AUTO setting where there is no device, the computer will always look to see if a device is plugged in at that location each time the computer boots. By changing this setting to NONE, the computer will boot slightly faster.
Advanced BIOS Features
Is it really necessary to thoroughly test your memory and floppy drive every single time you turn on the computer? Unless you suspect a problem with either one, I see no reason to continually test them with BIOS diagnostics. In this part of the BIOS we'll be able to reduce system start up time by enabling or disabling specific features - such as those just mentioned - to optimize the start-up process. Here are the recommended settings:
Boot Virus Detection : Enabled. Sometimes this is located under the Standard or Main section of some BIOS. While boot sector viruses are no longer the major threat they once were, enabling this feature will protect your data should you boot from an infected floppy disk or CD-ROM.
CPU Level 1 Cache : Enabled.
CPU Level 2 Cache : Enabled.
Quick Power On Self Test : Enabled. This will skip the repetitive memory count that occurs when you turn on your PC; chances are that if you really do have bad memory, this basic test won't catch it anyway.
First, Second, or Third Boot Device : Set your boot order, and disable any boot device here that you do not want to boot from.
Boot Other Device : Disabled, unless you are booting from a network or USB thumb drive
Boot Up Floppy Seek : Disabled. It's a waste of time and a noise maker.
Boot Up NumLock Status : Your choice. Some folks like the NumLock on their keyboard activated when Windows starts, while others want it disabled.
Gate A20 Option : FAST. While this feature is made more or less obsolete by Windows XP, it is still recommend you leave it on. Older versions of Windows and OS/2 perform better with this parameter set to FAST. The only reason someone would set it to normal would be if they are running DOS.
Typematic Rate Setting : Disabled. Your choice, really. This feature determines how long the keyboard waits when holding down a key until it starts repeating it, and how fast that happens.
APIC Mode : Enabled. This is the Advanced Programmable Interrupt Controller, which is responsible for multi-processor support, more IRQs, and faster interrupt handling.
OS/2 Onboard Memory > 64M : Disabled. This setting only applies to users running the now defunct OS/2 operating system from IBM.
Full Screen LOGO Show : Your choice. When enabled, the memory count and Power-On Self-Test (POST) are hidden behind a "curtain" - a graphic logo. For example, when you first turn on a Gateway computer, you might see GATEWAY in big letters across the screen. When disabled, the "normal" initiation sequence is displayed on the screen - the way most computers look when you first turn them on before the operating system begins to load. Some people prefer to hide the POST screen, while others prefer to always see it.
POST Complete Report : Your choice. This setting, when enabled, will display the results of the POST.
CPU and Memory Timings
Overclockers are PC enthusiasts who attempt to increase their system's performance by raising bus speeds and increasing their CPU speed beyond the figure at which it was sold and designed to run. They also quite frequently need to raise the voltage of these devices, since they are pushing them harder, which also generates more heat.
Overclocking can make a considerable difference to the performance of both your memory and CPU, but it will also void your CPU warranty, could cause complete system failure requiring component replacement, and can cause random system instability. For that reason, many of the frequency and voltage settings offered in this part of the BIOS should be left alone or set to AUTO.
CPU External Freq. (MHz) : Be sure to set this in accordance with the specifications of your processor.
CPU Frequency Multiple Setting : AUTO.
CPU Frequency Multiple : Be sure to set this in accordance with the specifications of your processor.
System Performance : Optimal.
CPU Interface : Optimal.
Memory Frequency : By SPD. Most memory-chip manufacturers include a Serial Presence Detect (SPD) chip, which reports to the computer's BIOS the size, data width, speed, and voltage of the installed memory. These settings are determined by the manufacturer to ensure maximum performance and reliability, so "By SPD" is considered a safe, recommended setting. By adjusting these settings yourself, you may be able to squeeze more performance out of your system, but if you're not careful, you might cause your system to constantly crash, not boot properly, or not boot at all
Memory Timings : Optimal.
FSB Spread Spectrum : Disabled. This feature helps systems pass European electromagnetic interference (EMI) tests. It accomplishes this by constantly varying, ever so slightly, the frequency of the Front Side Bus (FSB). Be warned that enabling this feature with large values can result in Internet connection disruption, as well as stability problems if you overclock your system.
AGP Spread Spectrum : Disabled. The description above applies here as well, except that this is for modulating the frequency of the Advanced Graphics Port (AGP) interface.
CPU VCore Setting : AUTO.
CPU VCore : Be sure to set this in accordance with the core voltage requirements of your processor.
Graphics Aperture Size : 64 MB or 128 MB. This feature controls the size of the Graphics Address Relocation Table (GART) and the amount of memory address space used for AGP memory addresses. Regardless of how much on-board memory a system's video card has, a setting of 64 MB or 128 MB is recommended. This will allow the video card to remain optimized in the event that an application requires more memory for texture storage, while simultaneously limiting the GART to a reasonable size.
AGP Frequency : AUTO.
System BIOS Cacheable : Disabled. You might be under the impression that all cache is good, but that's not true. This feature can cause problems such as system crashes if a program tries to write to the BIOS area being cached. This is a great feature to enable if you're still using DOS.
Video RAM Cacheable : Disabled. This option allows the Video RAM to be copied directly to your L2 cache, which is considerably faster to access than ROM. However, Windows is so much more advanced than DOS, Windows rarely ever uses this ROM. Because the L2 cache is quite limited in size, it is recommended you let Windows use the L2 cache for enhancing the efficiency of other tasks.
DDR Reference Voltage : This setting controls the voltage of the Double-Data Rate (DDR) memory in your system.
AGP VDDQ Voltage : 1.5V. VDDQ is an engineering term meaning Voltage between Drain and common for Data Quad-band. In English, this refers to how much voltage should be supplied to the video card.
AGP 8X Support : Enable this if the system's video card supports 8X AGP speeds.
AGP Fast Write Capability : Enabled is recommended. This feature, when enabled, allows the AGP device to bypass main memory when performing write transactions from the chipset to the AGP device, increasing performance by as much as 10 percent. However, some games and PCI cards may experience problems with this setting enabled.
Some BIOSes refer to the CPU Frequency Multiple as the CPU Multiplier. To understand what this means, realize that the CPU processes data at a different speed than the rest of your system. In this example, an AMD Athlon 2600 CPU is used, which runs at 2.133 GHz. It talks to the motherboard at 133.33 MHz, which is referred to as the Front Side Bus (FSB) speed. Therefore, 133.33 MHz (generally referred to as 133 MHz) is the FSB speed, while the CPU processes data at a multiple of 16 x 133.33 for a total of 2,133, or 2.133 GHz. So the multiplier is 16.
Through testing, AMD has determined - as have many independent magazines - that their 2.133 GHz CPU runs as fast as (or faster than) an Intel CPU rated at 2.6 GHz. Knowing that most consumers shop looking for large numbers to equate to performance, AMD had to come up with a way to convince consumers that even though their clock speed number was smaller, the processor's performance was the same or better than an Intel system with larger numbers. This explains why an AMD Athlon 2600 (as used in this example) actually runs at 2.1333 GHz and not the implied 2.6 GHz.
Integrated Peripherals
This section of the BIOS setup program contains settings for built-in peripherals included with the motherboard. This includes serial and parallel ports, as well as audio, LAN, and USB ports
. Unused ports that are enabled represent a significant drain on resources and should be disabled.
Primary VGA BIOS : This setting is used only when there are two video cards installed in the PC: One AGP (accelerated graphics port) and one PCI (peripheral component interconnect). The system wants to know which card to initialize first and make its "main" card. If you only have one video card, it is most likely AGP. For most people, the default setting is wrong and should be changed to AGP VGA Card . If you have two video cards, select the video card that you want to be the "main" or primary card. The primary video card will show the Windows splash screen and POST results during initial boot-up.
USB Controllers : This feature allows you to limit the functionality of the Universal Serial Bus (USB) controllers on your system. You may choose to allow only USB 1.1, USB 1.1 & 2.0, or disable USB altogether. Most people will want to set this to USB 1.1 & 2.0 for maximum versatility.
USB Legacy Support : This setting must be enabled if the PC has a USB keyboard and the user wants to use this keyboard either in a DOS environment or before the operating system loads (in boot menus, for example). If this setting is disabled, then booting to a floppy disk or CD-ROM will render the keyboard useless. Also, ironically, trying to enter the PC's BIOS may be impossible if this setting is disabled and a USB keyboard is connected. If the PC has a USB keyboard with a rectangular connector, then set this to Enabled . If it has a PS/2 keyboard (round connector), set this to Disabled . Be aware that enabling this feature may result in problems with the computer waking up from Standby or Hibernate mode, or cause the computer to not shut down properly. In other words, enable this only if you must.
USB Mouse Support : Same as above. Disabled is the preferred setting.
Onboard AC97 Audio Controller : If a sound card such as a Soundblaster Audigy has been added to the PC, or the system does not have speakers, be sure to Disable the motherboard's on-board sound card. This will free up precious resources and prevent potential conflicts. For most systems, however, this feature should be set to Enabled .
Onboard AC97 Modem Controller : Some motherboards are sold with built-in or proprietary dial-up modems. If the system lacks a modem, or if the modem is plugged into a standard PCI slot on the motherboard, then this setting should be Disabled. Otherwise, it should be Enabled.
Onboard LAN: This lets you enable or disable the built-in network interface card (NIC). The options are Auto or Disabled If your mainboard has two onboard NICS and you use only one, disable the one you are not using, to free up valuable resources.
Onboard 1394 Device (Firewire) : This feature enables or disables the built-in IEEE 1394 (Firewire) port on the PC. If the system does not have any Firewire devices, or if the Firewire connector is not plugged into the motherboard, disable this device to free up valuable resources.
Floppy Disk Access Controller : Most PCs today do not have floppy drives. If that's the case for your PC, or if you never use your floppy drive and would rather have resources available for other uses, then disable this device. Note: If you have a floppy drive and decide to disable it here, the drive will not function unless you go back in to the BIOS and re-enable it.
Onboard Serial Port 1 : Most people no longer use serial ports for connecting external peripherals, as most have been replaced by USB equivalents. If you do not use the system's serial ports, disable the ports and free up the resources. On the other hand, if you do use the serial port, then this option should be set to 3F8/IRQ4 .
Onboard Serial Port 2 : Same as above, if you do not use this. If you do use it, then set this to 2F8/IRQ3 .