BIOS Settings

The BIOS settings on your PC can make a significant difference to the performance of your PC and can even render devices or the netire PC unusable if inappropriately set. The following is a guide to the various settings available (some are not available on all BIOS's) and was compiled largely with reference to AWARD BIOS on an ABIT BE6-2 (non-RAID version): (Settings in red must be altered with extreme care as they can seriously and permanently damage the system)

CPU/Processor settings:

CPU/Processor operating frequency (clock speed) - This must be set to the rated speed of your processor for the CPU/Processor to be guaranteed to function correctly. The correct operating frequency can usually be found on the packaging which the CPU/Processor was supplied in or may be printed on the CPU/Processor itself. The speed is usually measured in MegaHertz (MHz) or GigaHertz (GHz) and is made up of a buss speed (Front-Side Buss - FSB) and a Multiplier:

CPU/Processor Front-Side Buss (FSB) clock/speed - This setting controls the clock speed of the Front-Side Buss which usually means the RAM/Memory. Newer SDRAM equipped PC's usually run the FSB at 133MHz whereas older PC's may run it at 100MHz. DDR-RAM and RAMBUS/RIMM's run different variations of speeds, often 'double pumped' (twice the applied clock speed). The setting made here must be appropriate to the rated speed of your RAM/Memory (e.g. PC100 = 100MHz, PC133 = 133MHz) and that which the CPU/Processor can function. Most popular CPU's/Processors are available in 100MHz and 133MHz (and possibly others) FSB ratings. Some Motherboards/Mainboards allow adjustment of this setting down to 1MHz increments (or even less) whilst some have pre-defined allowable values such as 66MHz, 100MHz, 133MHz etc.

Multiplier - The CPU/Processor clock speed is usually made up from the FSB speed (above) and this setting, the Multiplier. As you may expect, the CPU/Processor operating frequency is established by multiplying the FSB speed by the Multiplier e.g. a 100MHz FSB and a Multiplier of 8 would be used with an 800MHz CPU/Processor (which runs a 100MHz FSB). This setting is usually adjustable in steps of 0.5 or 1.

PCI Clock/CPU FSB Clock - This setting controls the speed at which the PCI buss is operated. The PCI buss is usually intended to be operated at 66MHz and an appropriate value of this setting must be chosen such that this is the case. This setting controls the ratio between the speed of the FSB and the speed of the PCI buss (e.g. if the FSB is 100MHz, the PCI Clock/CPU FSB Clock factor should be set as close as possible to 2/3 since 2/3 of 100MHz is 66.666MHz). If this setting is such that the PCI buss is operated at greater than 66MHz, stable operation of PCI devices such as Soundcards cannot be guaranteed.

AGP Clock/CPU FSB Clock - Similarly to the above PCI Clock/CPU FSB Clock setting, this setting controls the ratio between the AGP and the FSB buss speeds. The AGP buss, like the PCI buss is intended to be run at 66MHz and therefore the setting which gives an AGP Clock speed closest to this should be chosen (e.g. if the FSB is 100MHz, the AGP Clock/CPU FSB Clock setting should be as close to 2/3 as possible to give an AGP buss Clock speed of 2/3 of 100MHz = 66.666MHz).

AGP Transfer Mode - This setting controls the mode in which data is passed to the AGP buss. The 'Default' setting is normally fine but this should be set to 'Normal' if the FSB is 125MHz or more.

CPU Core Voltage - As you'd expect, this setting controls the Core Voltage of the CPU/Processor. This setting is crucial and whilst it is not normally required to be set manually, if it is set manually, the setting must as reccomended by the CPU/Procesor manufacturer (the setting can often be found on the manufacturers website).

I/O Voltage - This setting changes the voltage supplied to the system RAM/Memory and should usually be left on 'Default'.

In-Order Queue Depth - This sets the depth of the data queue used for the CPU's Cache. 1 can provide faster performance but may result in instability whereas 8 gives the most stable but slowest performance.

Level 2 Cache Latency - This setting adjusts the Level 2 (L2) cache speed. Larger values (range is usually 1 - 15) give faster operation but may also result in instability. Most systems should run fine on 14 or 15.

IDE HDD Detection - This setting is used to detect and set the appropriate parameters for each drive on the system. This setting can be set to 'Auto' if you don't want to set each drive up properly but better performance can be attained by setting each drive up properly. It is easy enough to do, there should be a function (somewhere) which can detect and set the appropriate values for each drive. Care must be taken if you are setting the parameters manually since the disk can be damaged if incorrect setting are used. Virtually all modern drives can be run in 'LBA' (Logical block Addressing) mode which offers optimum performance. Optical drives (CD/DVD drives) should be set to 'Auto' since they cannot usually be configured.

Floppy Mode 3 Support - This setting provides support for compatible 3 Mode (Japanese) Floppy disk drives. This is not often required to be enabled (unless you're Japanese or need to use a 3 Mode Floppy drive).

Video - This selects the Video mode of your Graphics card. Virtually all cards are VGA in some form and thus VGA or EGA/VGA (or the appropriate VGA extension such as SVGA) should be selected.

Halt On - This setting allows you to set what type of errors (if any) the system will halt on when booting up. The usual options are All Errors, No Errors, All except Keyboard, All except Disk & All except Disk or Keyboard. This setting should be set on 'All Errors' unless a persistant problem is encountered which halts booting but does not cause any other ill-effects.

Quick Power On Self Test (POST) - This setting controls whether or not the system will simplify it's check on the system RAM/Memory and peripherals on startup. Settings are enabled or disabled, disabled is reccomended since the system will then perform a full check (though this slows startup time slightly).

Virus Warning - This setting is normally disabled as default and this is usually the recommended setting. It warns the user if any software attempts to access the Hard-disk's boot sector or partition table and though this may be useful for detecting viruses, it also can prove annoying and disruptive when certain applications (e.g. bootmagic) are run.

CPU Level 1 Cache - This setting enables or disables the Level 1 Cache of the CPU/Processor(s). This setting should always (provided the CPU/Processor has Level 1 Cache - almost all do) be set to 'enabled' so that the CPU/Processor can take advantage of it's Level 1 Cache which speeds up it's operation by storing regularly used data addresses for quick access.

CPU Level 2 Cache - This should also be set to 'enabled' so that the CPU/Processor can take advantage of it's Level 2 Cache which also speeds up it's operation by storing regularly used data addresses for quick access.

CPU Level 2 Cache ECC Checking - This setting determines whether or not ECC (Error Checking and Correction) will be used on the Level 2 Cache. This should be set accordingly with the CPU's/Processor's Level 2 Cache capability (usually 'enabled').

Processor Number Feature - This setting allows or disallows programs to read the Processor Number of Intel Pentium 3 processors. If a Pentium 3 is installed, this should be set to 'enabled' if not, to 'disabled'.

First/Second/Third... Boot Device - This setting decides the first/second/third device in the boot-sequence (i.e. the order in which the system will attempt to boot). The Hard-disk containing Windows should be set as the first device. The order may need to be adjusted if re-installing windows (in order that the system can boot from the Windows CD or Floppy to start setup).

Boot other device - This allows the system to attempt to boot from another device if all three specified boot devices fail to boot.

Swap Floppy drive - This swaps drive A (Floppy 1)to be drive B (Floppy 2) without having to swap the cables around. This should usually be disabled.

Bootup Floppy Seek - This controls whether or not the system will display an error message if no Floppy drive is detected. This should usually be disabled.

Bootup Numlock Status - This control the status of the Numlock function on the keyboard upon booting. Settings are 'Off' or 'On' - set as desired.

Typematic Rate - This sets how often the keystroke will be repeated on holding down a key on the keyboard.

Typematic Delay - This sets the delay between pressing a key on the keyboard and when it begins to repeat.

OS Select For DRAM > 64MB - OS/2 (an operating system) requires that communication between itself and RAM/Memory over 64MB in size and thus if your are using OS/2 as your operating system, you should set this option to 'OS/2'. If however, as is more likely you are running Windows or Linux, you should set this to 'Non-OS/2' .

Report No FDD For Win95 - If running Windows 95 with no Floppy drive, you should set this to 'Yes' so that the BIOS can tell Windows 95 not to expect a Floppy drive, otherwise it should be set to 'No'.

Video BIOS Shadow - This feature controls whether or not the Video Card's BIOS is cached into RAM (which is faster than it's default state of being held in ROM). This feature should almost always be enabled which will greatly improve system performance.

Shadowing Address Ranges - This option allows you to enable an expansion card/device in the system to shadow it's BIOS (note that most cards/devices do not have BIOS with the usual exception of SCSI controller cards). This, like the Video BIOS Shadowing allows the selected card/device to operate faster. To achieve correct functionality, you must know the address range used to access the card/device's BIOS and that range must be available from the list displayed here.

Delay IDE Initial - This setting is for bootup compatability with older (and slower) IDE drives which the BIOS may fail to detect due to their lack of speed. The setting should only be used if bootup problems arise with an older drive and the delay should be started small and worked upwards until boot success is achieved.

NOTE: The following RAM settings are part of the specification you may see when buying SDRAM. Usually, you will be quoted a size of the SDRAM (e.g. 128MB) and three numbers (e.g. 3/3/3) - the following setting refer directly to those three numbers (which are sometimes combined into one number as they are almost always the same):

SDRAM RAS to CAS Delay - This setting allows you to adjust the RAS (Row Address Strobe) to CAS (Column Address Strobe) delay to fit the specifications of your RAM/Memory (Memory is arranged in a grid hence the row and column addresses). Usually you should set this value to 2 if you are using CAS 2 RAM/Memory or 3 if using CAS 3.

SDRAM RAS Precharge Time - This setting allows you to adjust the number of clock cycles for which an electrical charge is accumulated which is used to write to the RAM/Memory. If a sufficient number of clock cycles is not allowed, insufficient charge will accumulate and the data may fail to be written properly. Usually you should set this value to 2 if you are using CAS 2 RAM/Memory or 3 if using CAS 3.

SDRAM CAS Latency Time - This setting allows youy to adjust the CAS Latency to (usually) either 2 or 3 clock cycles. Usually you should set this value to 2 if you are using CAS 2 RAM/Memory or 3 if using CAS 3.

SDRAM Precharge Control - This setting decides whether Precharge is used on all or only re-tried failed SDRAM writes. If set to 'enabled', Precharge will only be used on re-tried failed writes. 'Disabled' means that Precharge will be used on all writes which slows down system operation but provides more stability.

DRAM Data Integrity Mode - This setting too should be set in accordance with the type os RAM/Memory used. A property of RAM/Memory which is only provided on slightly more expensive RAM/Memory is ECC (Error Checking and Correction) which provides some error detection and correction on data from RAM/Memory. If your RAM/Memory is ECC compliant, you should set this value to 'ECC', if not, set it to 'Non-ECC'. It's a good idea (if possible) to use ECC capable RAM/Memory.

System BIOS Cacheable - This provides a space in RAM/Memory for caching of the system BIOS allowing for faster operation. This can cause problems if a program or Windows writes to this area as this will corrupt the BIOS data which may well cause undesired (and very random) operation. That said, it should be fine to enable this feature but if you experience random problems/crashes, you may want to experiment with it.

Video BIOS Cacheable - This provides a space in RAM/Memory for caching of the Videocard's BIOS allowing for faster operation. This can cause problems if a program or Windows writes to this area as this will corrupt the Video BIOS data which may well cause undesired (and very random) operation. That said, it should be fine to enable this feature but if you experience random problems/crashes, you may want to experiment with it.

Video RAM Cacheable - This provides a space in RAM/Memory for caching of the Videocard's RAM allowing for faster operation. You should check whether your Videocard supports this feature before enabling it.

8 Bit I/O Recovery time - This setting adjust the delay between consecutive 8 Bit operations (which there probably won't be any of in a modern PC). You can probably set this value to N/A, it most likely will not be used (unless you have old cards installed).

16 Bit I/O Recovery time - This setting adjust the delay between consecutive 16 Bit operations. It can probably be set to N/A and it too will probably not be used since most modern cards are 32 or 64 Bit.

Memory Hole at 15-16M - This setting is used to allow a space in RAM/Memory of 1MB for some ISA expansion card's ROM. Try altering this setting if you have trouble with an ISA card which has onboard ROM.

Passive Release - This setting too can be experimented with if you are experiencing problems with an ISA card. It enables or disables the Passive Release function of the Intel PIIX4 PCI to ISA bridge.

Delayed Transaction - This function too provides timing compatability with the ISA buss. It must be enabled for the system to be PCI 2.1 (or greater) compliant which allows sharing of IRQ's.

AGP Aperture Size - This setting controls the maximum amount of system RAM/Memory that is available to be used by the AGP Videocard. The RAM/Memory will not be reserved for the Videocard but the card will use it if necessary. The reccomendation for this setting is to use a Videocard with a large amount (at least 16MB, preferably 32 or 64Mb) of RAM/Memory onboard and to then set this value to 32MB or less dependant on the amount of RAM/Memory you have installed.

SDRAM Leadoff Command - This setting must be made in accordance with your SDRAM's SPD capability. If you are using fast (CAS 2) SDRAM, you may well be able to set this to the highest value available (usually 4 which gives the fastest performance).

Onboard Parallel Port - This setting is of vital importance to Cubase users due to the dongle used for copy-protection. In order to be compatible with the dongle, EPP must be selected for the Mode - the version of EPP (1.7 or 1.9) is not usually important.

ACPI - ACPI (Advanced Configuration and Power Interface) is reccomended to be disabled. The 'Video Off After' function too should be disabled (set to N/A). This ensures that components of the PC will not be closed down unexpectedly and renders all other ACPI related settings redundant.

Modem use IRQ - If you have no Modem, set this to N/A and you will free up a potential IRQ for other uses. It may be worth reserving a specific IRQ here if you need to (though Windows will probably ignore it anyway).

PNP OS Installed - Set this to 'Yes' to allow Windows control over IRQ and other resources.

Force Update ESCD - This setting should be disabled unless there is a resource conflict which renders Windows unable to boot.

Resources Controlled by - This setting controls whether the system (Auto/ESCD) or you (Manual) control the system resource settings (IRQ's and the like). Usually you can leave this set to Auto/ESCD but if you need to manually specify resources, set it to 'Manual' (Note: You may want to set 'PNP OS Installed' to 'No' so that Windows doesn't have control over resources either).

Reserve Memory Base - This setting reserves some RAM/Memory for ISA devices - set this to N/A if you have no ISA devices or you have no problems with your ISA devices - otherwise, experiment.

Reserve Memory Length - Controls the amount of RAM/Memory reserved above - experiment if you are reserving RAM/Memory.

PCI/VGA Pallet Snoop - This allows the BIOS to look at and alter VGA data - this should only be used if you're experiencing problems with a MPEG card.

Assign IRQ for VGA - This setting assigns (and reserves) an IRQ for a PCI Videocard. Set this to 'disabled' unless you use a PCI Videocard.

Assign IRQ for USB - This setting assigns (and reserves) an IRQ for the USB controller. Set this to 'disabled' unless you use USB devices.