General BIOS Informations

BIOS stands for Basic Input Output System  but it could also have been meaning "Basic Initial Operating System" and it would have been true because the BIOS is what is first loaded when you start your computer. As a matter of fact the BIOS is where are kept all you computer hardwares basic informations which are the first informations read and required when you first turn on your computer.

The BIOS informations are stored in a CMOS chip which is kept under constant voltage supply by the computer backup battery. This way the informations containned in the CMOS are allways alive even if the computer power is turned off.

The listing below is showing all the informations stored into the BIOS;

  • Time and Date
  • Number of Floppy Disk Drives
  • Floppy Disk Drives informations (size, number of track, sectors, head, ect)
  • Number of Hard Disk Drives
  • Hard Disk Drives informations (size, number of track, sectors, head, mode, ect)
  • Number of CD-ROM Drives
  • CD-ROM Drives informations (operating mode, ect)
  • Boot sequence ( Enable the user to decide what disk will be checked first when booting)
  • Cache Memory informations (size, type, timing, ect)
  • Main Memory Informations (size, type, timing, ect)
  • ROM Shadowing informations (Enabling or disabling of Video and System ROM shadow)
  • Basic Video mode informations (EGA, VGA, ect)
  • Setting of PCI and ISA slots
  • AGP Port Settings (aperture size, ect)
  • Virus Protection Warning
  • Setting of COM Ports (Enabling or disabling of Com port 2 for instance)
  • Password Protection (enable the user to set his password)
  • Energy saving informations (snooze modes for the HDD and monitor)

Depending on your BIOS type there could be many alot of other information not listed above that can possibly be stored in the BIOS memory. Note that some of the information in the above list may not be a part of the BIOS installed on your computer.

Because the BIOS contains all of the information about the memory, most of the performance optimization of a computer can be obtained by adjusting the BIOS settings. However, this is a very tricky process, especially for those without any BIOS setting knowledge.


Before changing anything in your BIOS settings you should write down all of your current settings and save them in case you need to bring back the BIOS to the original values. It is not uncommon to have a total system crash when changing the BIOS settings, so if you don't note the original values it could be very difficult to get your system to work again!

Furthermore, you must note the value of the settings you will change every time you make a change so if the last value you tried doesn't work, and causes your computer to stall (or just doesn't bring any performance improvement) you will be able to come back to the preceding value without any problems.

Believe me, its the only way to do it efficiently unless you have a cybernetic memory !


Most BIOS contains a hard disk utility labelled "Low Level Formating". All IDE/ATA or SCSI drives virtually installed on every modern PC built after 1992 or about could be permanently damaged by using this feature. This utility has only been designed to work with the old MFM and RLL disks drives used from about 1980 to about 1992 !

Advanced CMOS Setup

Before we step into the advanced chipset setup, there are some very interesting CMOS setup features to consider. I will introduce them to you so you will know what to do with them.

Internal Cache Memory

The internal cache is a memory area located inside of the CPU. This memory is also referred to as the L1 cache. This type of memory is faster than the external cache memory.

Suggestion: Enabled unless you want to slow down your computer by about 15% !.

External Cache Memory

The external cache memory is an area between the CPU and the system bus where some very high speed memory is located to store frequently requested instructions. Most Pentium systems have either 256k or 512K of external cache and some Pentium IIs can handle up to 1meg of external cache. The external cache is also referred to as the L2 cache.

Suggestion: Enabled. Disabling this setting will sacrifice a large amount of your computer performance.

Fast Gate A20 Option

This option uses the fast gate A20 line, supported in many chipsets, to access the memory above 1 MB. Using this option will make the memory access faster than when this setting is not enabled. This option is very useful in networking and multitasking operating systems.

Suggestion: Enable and check to see the improvement.

System ROM Shadow

This setting will copy the contents of the system ROM into the RAM memory so the RAM memory will be used instead of the system ROM memory, and doing so will give a significant performance increase.

Suggestion: Enabled recommended for improved performance.

Video ROM Shadow

This setting will copy the contents of the video ROM into the RAM memory so the RAM memory will be used instead of the video ROM memory and doing so will give a significant performance increase.

Suggestion: Enabled recommended.

Note: If your graphics card is equipped with a Flash-BIOS you can disable this setting because Flash-BIOS are accessed at speeds close to RAM memory, so it might be interesting to save this RAM memory space to use it for something else. However, on motherboard where the BIOS automatically uses 384K of RAM it wont save any memory space whether or not you use shadowing. So in this case enabled is recommended even if your graphics card is using Flash-BIOS!

Advanced Chipset Setup


Never try to change all the settings at once! It's a much better approach to change one setting, then test your system using some benchmark tools, note the differences and try another setting.

Auto Configuration

This default factory setting is used to set the BIOS to supposedly give you the best overall computer performance, but we all know that this is not exactly true. As a matter of fact, the Auto Configuration setting uses very conservative memory timing to make sure the computer will operate in a more stable condition and won't crash or freeze for most of the worst conditions it might encounter while running some very demanding applications.

However, if you really want to get the most out of your computer this setting must be disabled because you wont be allowed to tweak your memory timings when the Auto Configuration is enabled !

The Fixed Timing or Manual Setting

Even if I would classify this setting in the automatic category, it is really a manual setting because it usually is not enabled by default and you must choose the values that it will work with yourself.

When you enable this setting you are forced to choose a memory timing which must precisely correspond to the actual main memory timing installed on your motherboard. As a general rule there are only 3 possibilities offered and they are 70ns and 60ns and no value. To access these settings, the Auto Configuration setting must be disabled. Enabling this setting will allow the system to use some predetermined memory timing for you.

Using the "no value" setting will allow you to tweak each of your memory timings separately, which is what we are looking for. Therefore, disabling this setting to use the "no value" setting is obligatory if you wish to set your own memory timings!

Explanation of the "RAS" and "CAS" terms

Before you go any further I would like to give you the definition of these two terms, because they will be widely used in the memory timing information. The memory is read from and/or written to using data bursts which will be stored in the memory architecture divided into columns and rows. According to this RAS stands for "Row Access Strobe" and CAS stands for "Column Access Strobe".

The Memory Timing Settings

DRAM CAS Timing Delay

DRAM is organized by rows and columns and accessed through strobes. When a memory read or write access is performed, the CPU activates the "Row Access Strobe" to find the row containing the required data. Afterwards, a "Column Access Strobe" specifies the column. RAS and CAS are used to identify a location in a DRAM chip.

Suggestion: The default CAS is no delay but if you have slow DRAM memory you should use a value of 1 state delay.

DRAM Read Timing

Memory reading of stored data is accomplished using specific memory words called "DWords". To speed-up the reading process a set of 4 or 8 of these "DWords" are read in a sequence.

In clock cycles it gives x-y-y-y where the y corresponds to the DRAM Read timing.

EDO memory modules normally use x222 and x333 while FPM memory uses x333 and x444. Usually these settings are offered by the mean of combined values like x222/x333 or x333/x444, where the higher values are for FPM memory and the lower values for EDO DRAM memory.

Suggestion: Try the lowest values and if you don't have any problems after running your most demanding applications then it looks like it is the right setting for your memory! If your computer experiences crashes, freezes or even refuses to boot, come back to a higher value.

DRAM Write Timing

This setting is used for the write timings and is applied to both FPM and EDO memory.

Suggestion: Try the lowest values possible. Test your system and again if your computer experiences crashes, freezes or even refuses to boot, come back to a higher value.

RAS Active Time

The is the amount of time a RAS can be kept open for multiple accesses.

Suggestion: High figures will improve the performance.

RAS to CAS Delay

This is indicating the amount of time a CAS is performed after a RAS.

Suggestion: The lower the better depending on your memory type and quality. If you have problems then come back to a higher value.

DRAM R/W Leadoff Timing

This parameter controls how many clock cycles are required for the first access to memory during a read "burst". It's the 'x' of the previously described read and/or write timings.

Note that this setting is somewhat different depending on your chipset. For instance, some chipset's fastest setting is 7-y-y-y while some others can go as low as 5-y-y-y - therefore making them faster !

Suggestion: The lower this setting, the faster your system will work. How low you can set this setting depends on your bus speed and memory quality. Putting this setting too low could cause memory errors. ! So, as usual make the change and test your system!

Note: The value '5' is supposed to be used only with 50ns memory or faster.

DRAM Speculative Leadoff

This is a performance enhancement available with some chipsets to speed up the first access to system memory. The memory controller sort of "cheats" by starting the initial read request before the address for the read has been completely resolved.

Suggestion: For best efficiency you will normally enable this setting. If doing so causes instability then disable it !

Turbo Read Leadoff

This setting is used to shorten the leadoff cycles and optimize performance in cacheless, 50-60 MHz, or one-bank EDO DRAM systems.

Suggestion: Enabling this setting is likely to improve performance but as usual be careful to test and see what happens!

Turn-Around Insertion

When enabled, it inserts an extra clock cycle (wait state) between consecutive DRAM read cycles.

Suggestion: Normally the system can perform back-to-back burst reads without this extra delay, and the default for this setting is "Disabled" so keeping it this way is a good idea!.

Turbo Read Pipelining

When this setting is equal to 1 (or enabled) the system bypasses the first register in the DRAM data pipeline thus saving one clock cycle. However, this setting may only be used in a cacheless configuration!

Suggestion: Enable if you're working cacheless but according to this information enabling this setting on a cache enabled system should have no noticeable effects!

Speculative Lead Off

To reduce read latencies which can slow the memory performance, some chipsets are allowing read requests before the address has been completely retrieved.

Suggestion: Disabling this setting will prevent the chipset to gain profits of this feature while enabling it will give additional performance boost! Don't forget to apply the usual security rules so test your system and if the results are positive keep it this way!

Peer Concurrency

Enabling this setting will allow multiple PCI devices to run simultaneously.

Suggestion: This setting is Enabled by default. However this might reduce the system resources available for other tasks so you will have to see yourself what gives the best results.

System ROM Cacheable

When the system BIOS ROM has been shadowed by copying its contents into the motherboard main RAM memory, enabling this setting will further improve the performance by caching this RAM memory area.

Suggestion: Enabled recommended for improved performance.

Video ROM Cacheable

If the video BIOS ROM has been shadowed by copying its contents into the motherboard main RAM memory, enabling this setting will further improve the performance by caching this RAM memory area.

Suggestion: Enabled recommended.

Chipset NA# Asserted

Selecting enabled permits pipelining, in which the chipset signals the CPU for a new memory address before all data transfers for the current cycle are complete, resulting in faster performance.

Suggestion: Enabled is highly recommended.

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