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Small changes produce large effects

A significant improvement in system performance can result from the successful tweaking of BIOS settings, especially memory timings. They are accessed via the BIOS.

The improvements you can make will depend on the degree of access allowed by your BIOS type, and the PC components.

BIOS [1]

Basic Input Output Software

BIOS (Basic Input Output Software) BIOS information is kept in a ROM (Read Only Memory) chip on the system motherboard. The BIOS is permanently used on bootup to initiate communication between the hardware and the operating system (DOS or, nowadays, Windows 95).

The BIOS chipset is maintained by the computer's battery - a substantially incorrect clock time may well be a sign of deteriorating battery power.

When the PC starts, the BIOS performs diagnostics, and sets the operational characteristics of important items in the computer. Keep in mind that your system could possibly run faster (and better), with a few minor changes to hardware and software settings. Not all systems work the same way or have the same components, so it is not possible to predict the effect of any modification on a particular system.

Modern computers use Flash chips that can be upgraded via software.
The BIOS is accessed via a set of menus called the CMOS set-up.

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BIOS [2]

More on BIOS

At power on, an electric charge powers-up the CPU and starts the read-only memory BIOS. This begins the POST (Power On Self Test). POST is a set of tests that make sure all the computer components are working correctly and identifies their special characteristics - the RAM, internal drives, monitor, keyboard, others - if not found (or faulty) then you get beep(s) or an on-screen message.

Now it looks for an operating system e.g. DOS, Windows 95/98, etc. - first in the floppy drive, and, if not found, then in the hard disk. The pathway from here depends on the OS used.

BIOS continues to be active while the computer is in operation - it acts as an interface between software calls and the hardware required e.g. the keyboard.

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BIOS [3]

If booting with DOS

In DOS-based systems:

Employs POST (as above)

Loads the boot record (and loads IO.sys, Sysinit, Msdos.sys, into RAM).

OS then runs Config.sys.

Also loads and runs (input/output functions, some DOS internal commands)
Also runs Autoexec.bat.

System completes its installation, and the command prompt appears.

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BIOS [4]

If booting with Windows 95 / 98 systems:

In Win-based systems:

Employs POST (as above), which also checks for 'Plug-and-Play' devices.

Runs the IO.sys program.
Reads the Msdos.sys file (controls several of Win95's startup options).
Checks for Config.sys and Autoexec.bat files, and runs each (if present).

Now moves on to the Registry - User.dat and System.dat. This contains system's configuration, Windows 95 settings, information on various programs, personal settings, such as passwords, desktop configurations, and start menu folders. Interrupt request lines (IRQs) and devices.

Now the Windows 95 protect-mode drivers load, the Plug-and-Play information gathered during the POST is processed, and the Windows 95 graphical user interface (GUI) loads (including Password prompt if in use).

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BIOS [5]

BIOS Type:

When starting your computer you will see onscreen something like "AMI BIOS version xxxx ". This shows the manufacturer, and version, of your BIOS.

You can use CTBIOS to find your board manufacturer
and visit Wim's BIOS page to view a long list of BIOS updates
Wim's Page

If there is a fault (for many possible reasons) the computer will not boot and you will hear more than one beep.

Each BIOS manufacturer has its own beep codes.

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BIOS [6]

Sample beeps for AMI BIOS:

Check your manual and/or the BIOS manufacturer's site. In the event of a problem always first check all connections, and reseat all motherboard components.

No Beeps Power supply, or motherboard, or PC speaker
Two Beeps Memory problems.
Three Beeps Similar to two beeps
Four Beeps Problem with the system timer
Five Beeps CPU problem
Six Beeps Keyboard - gate A20 switch
Seven Beeps CPU - interrupt failure error
Eight Beeps Video card
Nine Beeps BIOS itself
Ten Beeps CMOS problem
Eleven Beeps Bad Level2 cache

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BIOS [7]

BIOS settings (the CMOS set-up) can be accessed, and then altered, by pressing a special key combination in the early stage of boot-up (often DEL, ESC, CTRL-ESC, F1, or CTRL-ALT-ESC) - the combination depends on the manufacturer. It is very important to know this if the computer won't boot as a result of a lack of caution on your part.

The time will come when your CMOS will loose its settings and your PC will stop working! Every PC users should have a note of all the settings in the BIOS - just in case! At first just make a note of the settings and exit without making any changes. Some thoughtful vendors supply a printout of the settings with new systems.

While having a look, remember that these screens affect the most basic system level elements of your computer. Do not make changes unless you feel sure what the result will be. Making changes is relatively easy using the arrow keys. If something goes wrong, you just reboot and go back into the BIOS to correct your modifications.

Making alterations is a safe procedure PROVIDED you make a copy of both the original settings and your changes.

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BIOS [8]

Often there are three or four main input screens in the CMOS set-up for the BIOS. They will, or should, have been set correctly by the manufacturer. Nevertheless they should be checked. They usually include:

Basic settings
Chipset settings
Local bus adjustments

Basic settings

These include the date, time, what types of drives are in your computer, how much memory is in your computer, etc.
All of these settings must agree with the actual components in your computer.

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BIOS [9]

System settings

For fastest performance make sure:
CPU speed is set to " fast "
• all caches are enabled (L1 and L2, memory)
• the FPU is enabled (Floating Point Unit)
• any Power conservation is disabled
• options such as PIO mode or Block transfer are turned ON (up to 10% improvement). PIO mode should be set to 3 or higher. BIOS settings may cause 32-bit disk access to work improperly. Many hard disk controllers don't use the more sophisticated options available when a hard disk is first installed. If your BIOS settings offer hard disk controller options turn them ON.
Memory shadowing: Only adjust memory shadowing if you are comfortable doing so, and are not short of memory. It can improve performance, but may possibly conflict with memory managers or other system settings. System slowdowns can occur when full memory shadowing isn't turned on. If problems occur just rectify the change - if that works, then you know the cause of the problem.

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BIOS [10]

Chipset settings

You may be able to adjust timings that will speed up your entire system. Lower the Wait states- see Tweak RAM timings & Video (next page)

Local bus adjustments

If your system has local bus (LB) architecture you may be able to adjust whether the local bus or the normal ISA slots have priority for system activity - and possibly some other adjustments.
Look for a BIOS option like " use maximum performance setting ".
• After making any adjustments to the BIOS, save your changes as you exit. Your system should continue the boot process by executing the remaining BIOS commands, and then the config.sys and autoexec.bat files (if present).
Warning: You should not change anything that refers to hard disk type - you may not be able to reboot until the correct type is re-entered.
Remember that quite small changes to BIOS have a major impact on performance.

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BIOS [11]

Update the computer BIOS

A BIOS update is often available from the manufacturer, or PC supplier.

You should keep up to date, but expect only a small, if any, speed improvement by doing so.

If you are concerned about your BIOS in relation to the Y2K problem, then you should contact your manufacturer immediately.

Flash BIOS updates for Intel motherboards can be found at Another good source for drivers and information on Intel motherboards is

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Please remember that you alone are responsible for the consequences of any changes you make to your computer hardware or software.

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