TURINYS
ABOUT BIOS 6
How BIOS Works 6
What BIOS Does 6
Booting the Computer 8
Configuring BIOS 9
Updating Your BIOS 10
Bootstrap Management 11
Boot Other Device 11
Boot Sequence 11
Boot Sequence EXT Means 12
Boot To OS/2 12
Boot Up Floppy Seek 12
Boot Up NumLock Status 13
Delay IDE Initial 13
First Boot Device 14
Init Display First 14
Primary Graphics Adapter 15
Primary VGA BIOS 15
Quick Boot 16
Quick Power On Self Test 16
Report No FDD For Win95 17
Reset Configuration Data 17
Resource Controlled By 18
Second Boot Device 18
Third Boot Device 19
Graphics Subsystem 19
AGP 2X Mode 19
AGP 4X Drive Strength 20
AGP 4X Mode 20
AGP 8X Mode 20
AGP Always Compensate 21
AGP Aperture Size 21
AGP Clock / CPU FSB Clock 22
AGP Drive Strength 22
AGP Drive Strength N Ctrl 23
AGP Drive Strength P Ctrl 23
AGP Driving Control 24
AGP Driving Value 24
AGP Fast Write 25
AGP ISA Aliasing 25
AGP Master 1WS Read 25
AGP Master 1WS Write 26
AGP Prefetch 26
AGP Secondary Lat Timer 26
AGP Spread Spectrum 27
AGP to DRAM Prefetch 28
AGPCLK / CPUCLK 28
DBI Output for AGP Trans. 28
Graphic Win Size 29
No Mask of SBA FE 30
PCI/VGA Palette Snoop 30
Post Write Combine 31
USWC Write Posting 31
Video BIOS Cacheable 32
Video BIOS Shadowing 33
Video Memory Cache Mode 34
Video RAM Cacheable 34
Memory Subsystem 35
Act Bank A to B CMD Delay 35
Delay DRAM Read Latch 36
DRAM Act to PreChrg CMD 37
DRAM Data Integrity Mode 37
DRAM Idle Timer 38
DRAM Interleave Time 38
DRAM PreChrg to Act CMD 39
DRAM Ratio (CPU:DRAM) 39
DRAM Ratio H/W Strap 40
DRAM Read Latch Delay 41
DRAM Refresh Rate 42
Fast R-W Turn Around 42
Force 4-Way Interleave 42
Gate A20 Option 43
MD Driving Strength 44
Memory Hole At 15M-16M 44
OS Select For DRAM > 64MB 45
OS/2 Onboard Memory > 64M 45
Read-Around-Write 46
Read Wait State 46
Refresh Interval 47
Refresh Mode Select 47
SDRAM 1T Command 48
SDRAM 1T Command Control 48
SDRAM Bank Interleave 49
SDRAM Burst Len 50
SDRAM Burst Length 50
SDRAM CAS Latency Time 50
SDRAM Command Rate 51
SDRAM Cycle Length 51
SDRAM Cycle Time Tras/Trc 52
SDRAM Idle Limit 52
SDRAM RAS Precharge Time 53
SDRAM RAS Pulse Width 53
SDRAM RAS-to-CAS Delay 54
SDRAM Row Active Time 54
SDRAM Tras Timing Value 55
SDRAM Trp Timing Value 55
Super Bypass Mode 56
Super Bypass Wait State 56
SuperStability Mode 57
Miscellaneous 58
Anti-Virus Protection 58
Duplex Select 58
Flash BIOS Protection 59
Floppy 3 Mode Support 59
Hardware Reset Protect 59
KBC Input Clock Select 60
Onboard IR Function 60
Onboard Parallel Port 60
Onboard Serial Port 1 61
Onboard Serial Port 2 61
Onboard USB Controller 62
Parallel Port Mode 62
Power On Function 63
RxD, TxD Active 63
Security Setup 64
Spread Spectrum 64
USB Controller 65
Virus Warning 65
Processor 66
Athlon 4 SSED Instruction 66
Auto Turn Off PCI Clock Pin 66
Clock Throttle 67
Compatible FPU OPCODE 67
CPU Drive Strength 68
CPU Fast String 68
CPU Hyper-Threading 68
CPU L2 Cache ECC Checking 69
CPU Level 1 Cache 69
CPU Level 2 Cache 70
CPU Level 3 Cache 70
CPU Thermal-Throttling 71
CPU VCore Voltage 71
Delay Prior To Thermal 72
FPU OPCODE Compatible Mode 73
Host Bus In-Order Queue Depth 73
Hyper-Threading Technology 74
In-Order Queue Depth 74
IOQD 75
K7 CLK_CTL Select 76
L3 Cache 77
Level 2 Cache Latency 77
N/B Strap CPU As 78
Processor Number Feature 79
S2K Bus Driving Strength 79
S2K Strobe N Control 80
S2K Strobe P Control 80
Speed Error Hold 81
Storage Subsystem 81
32-bit Disk Access 81
32-bit Transfer Mode 82
ATA100RAID IDE Controller 82
HDD S.M.A.R.T. Capability 82
IDE Bus Master Support 83
IDE HDD Block Mode 84
Master Drive PIO Mode 84
Master Drive UltraDMA 85
Onboard FDD Controller 86
Onboard IDE-1 Controller 86
Onboard IDE-2 Controller 87
PCI IDE Busmaster 87
Swap Floppy Drive 88
System Bus 88
16-bit I/O Recovery Time 88
8-bit I/O Recovery Time 89
AT Bus Clock 89
Auto Detect DIMM/PCI Clk 90
Byte Merge 90
CPU to PCI Post Write 90
CPU to PCI Write Buffer 91
Delayed Transaction 91
Disable Unused PCI Clock 92
FSB Spread Spectrum 92
ISA 14.318MHz Clock 93
ISA Enable Bit 93
Master Priority Rotation 94
P2C/C2P Concurrency 94
Passive Release 95
PCI 2.1 Compliance 95
PCI Chaining 96
PCI Clock / CPU FSB Clock 97
PCI Delay Transaction 98
PCI Dynamic Bursting 99
PCI IRQ Activated By 99
PCI Latency Timer 100
PCI Master 0 WS Read 100
PCI Master 0 WS Write 101
PCI Master Read Caching 101
PCI Pipelining 101
PCI Prefetch 102
PCI Target Latency 102
PCI to DRAM Prefetch 103
PCI#2 Access #1 Retry 103
Split Lock Operations 104
Synchronouse Mode Select 104
VLink 8X Support 104
System Resource Management 105
APIC Function 105
Assign IRQ For USB 105
Assign IRQ For VGA 106
ECP Mode Use DMA 106
EPP Mode Select 106
Force Update ESCD 107
Interrupt Mode 107
MPS Control Version For OS 108
MPS Revision 108
PIRQ x Use IRQ No. 109
PNP OS Installed 109
ABOUT BIOS
How BIOS Works
One of the most common uses of Flash memory is for the basic input/output system of your computer, commonly known as the BIOS (pronounced „bye-ose“). On virtually every computer available, the BIOS makes sure all the other chips, hard drives, ports and CPU function together.
Every desktop and laptop computer in common use today contains a microprocessor as its central processing unit. The microprocessor is the hardware component. To get its work done, the
microprocessor executes a set of instructions known as software (see How Microprocessors Work for details). You are probably very familiar with two different types of software:
• The operating system – The operating system provides a set of services for the applications running on your computer, and it also provides the fundamental user interface for your computer. Windows 98 and Linux are examples of operating systems. (See How Operating Systems Work for lots of details.)
• The applications – Applications are pieces of software that are programmed to perform specific tasks. On your computer right now you probably have a browser application, a word processing application, an e-mail application and so on. You can also buy new applications and install them.
It turns out that the BIOS is the third type of software your computer needs to operate successfully. In this article, you’ll learn all about BIOS — what it does, how to configure it and what to do if your BIOS needs updating.
What BIOS Does
The BIOS software has a number of different roles, but its most important role is to load the operating system. When you turn on your computer and the microprocessor tries to execute its first instruction, it has to get that instruction from somewhere. It cannot get it from the operating system because the operating system is located on a hard disk, and the microprocessor cannot get to it without some instructions that tell it how. The BIOS provides those instructions. Some of the other common tasks that the BIOS performs include:
• A power-on self-test (POST) for all of the different hardware components in the system to make sure everything is working properly
• Activating other BIOS chips on different cards installed in the computer – For example, SCSI and graphics cards often have their own BIOS chips.
• Providing a set of low-level routines that the operating system uses to interface to different hardware devices – It is these routines that give the BIOS its name. They manage things like the keyboard, the screen, and the serial and parallel ports, especially when the computer is booting.
• Managing a collection of settings for the hard disks, clock, etc.
The BIOS is special software that interfaces the major hardware components of your computer with the operating system. It is usually stored on a Flash memory chip on the motherboard, but sometimes the chip is another type of ROM. BIOS uses Flash memory, a type of ROM.
When you turn on your computer, the BIOS does several things. This is its usual sequence:
1. Check the CMOS Setup for custom settings
2. Load the interrupt handlers and device drivers
3. Initialize registers and power management
4. Perform the power-on self-test (POST)
5. Display system settings
6. Determine which devices are bootable
7. Initiate the bootstrap sequence
The first thing the BIOS does is check the information stored in a tiny (64 bytes) amount of RAM located on a complementary metal oxide semiconductor (CMOS) chip. The CMOS Setup provides detailed information particular to your system and can be altered as your system changes. The BIOS uses this information to modify or supplement its default programming as needed. We will talk more about these settings later.
Interrupt handlers are small pieces of software that act as translators between the hardware components and the operating system. For example, when you press a key on your keyboard, the signal is sent to the keyboard interrupt handler, which tells the CPU what it is and passes it on to the operating system. The device drivers are other pieces of software that identify the base hardware components such as keyboard, mouse, hard drive and floppy drive. Since the BIOS is constantly intercepting signals to and from the hardware, it is usually copied, or shadowed, into RAM to run faster.
Booting the Computer
Whenever you turn on your computer, the first thing you see is the BIOS software doing its thing. On many machines, the BIOS displays text describing things like the amount of memory installed in your computer, the type of hard disk and so on. It turns out that, during this boot sequence, the BIOS is doing a remarkable amount of work to get your computer ready to run. This section briefly describes some of those activities for a typical PC.
After checking the CMOS Setup and loading the interrupt handlers, the BIOS determines whether the video card is operational. Most video cards have a miniature BIOS of their own that initializes the memory and graphics processor on the card. If they do not, there is usually video driver information on another ROM on the motherboard that the BIOS can load.
Next, the BIOS checks to see if this is a cold boot or a reboot. It does this by checking the value at memory address 0000:0472. A value of 1234h indicates a reboot, and the BIOS skips the rest of POST. Anything else is considered a cold boot.
If it is a cold boot, the BIOS verifies RAM by performing a read/write test of each memory address. It checks the PS/2 ports or USB ports for a keyboard and a mouse. It looks for a peripheral component interconnect (PCI) bus and, if it finds one, checks all the PCI cards. If the BIOS finds any errors during the POST, it will notify you by a series of beeps or a text message displayed on the screen. An error at this point is almost always a hardware problem.
The BIOS then displays some details about your system. This
includes information about:
• The processor
• The floppy drive and hard drive
• Memory
• BIOS revision and date
• Display
Any special drivers, such as the ones for small computer system interface (SCSI) adapters, are loaded from the adapter, and the BIOS displays the information. The BIOS then looks at the sequence of storage devices identified as boot devices in the CMOS Setup. „Boot“ is short for „bootstrap,“ as in the old phrase, „Lift yourself up by your bootstraps.“ Boot refers to the process of launching the operating system. The BIOS will try to initiate the boot sequence from the first device. If the BIOS does not find a device, it will try the next device in the list. If it does not find the proper files on a device, the startup process will halt. If you have ever left a floppy disk in the drive when you restarted your computer, you have probably seen this message. This is the message you get if a floppy disk is in the drive when you restart your computer.
The BIOS has tried to boot the computer off of the floppy disk left in the drive. Since it did not find the correct system files, it could not continue. Of course, this is an easy fix. Simply pop out the disk and press a key to continue.
Configuring BIOS
In the previous list, you saw that the BIOS checks the CMOS Setup for custom settings. Here’s what you do to change those settings.
To enter the CMOS Setup, you must press a certain key or combination of keys during the initial startup sequence. Most systems use „Esc,“ „Del,“ „F1,“ „F2,“ „Ctrl-Esc“ or „Ctrl-Alt-Esc“ to enter setup. There is usually a line of text at the bottom of the display that tells you „Press ___ to Enter Setup.“
Once you have entered setup, you will see a set of text screens with a number of options. Some of these are standard, while others vary according to the BIOS manufacturer. Common options include:
• System Time/Date – Set the system time and date
• Boot Sequence – The order that BIOS will try to load the operating system
• Plug and Play – A standard for auto-detecting connected devices; should be set to „Yes“ if your computer and operating system both support it
• Mouse/Keyboard – „Enable Num Lock,“ „Enable the Keyboard,“ „Auto-Detect Mouse“…
• Drive Configuration – Configure hard drives, CD-ROM and floppy drives
• Memory – Direct the BIOS to shadow to a specific memory address
• Security – Set a password for accessing the computer
• Power Management – Select whether to use power management, as well as set the amount of time for standby and suspend
• Exit – Save your changes, discard your changes or restore default settings CMOS Setup
Be very careful when making changes to setup. Incorrect settings may keep your computer from booting. When you are finished with your changes, you should choose „Save Changes“ and exit. The BIOS will then restart your computer so that the new settings take effect.
The BIOS uses CMOS technology to save any changes made to the computer’s settings. With this technology, a small lithium or Ni-Cad battery can supply enough power to keep the data for years. In fact, some of the newer chips have a 10-year, tiny lithium battery built right into the CMOS chip!
Updating Your BIOS
Occasionally, a computer will need to have its BIOS updated. This is especially true of older machines. As new devices and standards arise, the BIOS needs to change in order to understand the new hardware. Since the BIOS is stored in some form of ROM, changing it is a bit harder than upgrading most other types of software.
To change the BIOS itself, you’ll probably need a special program from the computer or BIOS manufacturer. Look at the BIOS revision and date information displayed on system startup or check with your computer manufacturer to find out what type of BIOS you have. Then go to the BIOS manufacturer’s Web site to see if an upgrade is available. Download the upgrade and the utility program needed to install it. Sometimes the utility and update are combined in a single file to download. Copy the program, along with the BIOS update, onto a floppy disk. Restart your computer with the floppy disk in the drive, and the program erases the old BIOS and writes the new one. You can find a BIOS Wizard that will check your BIOS at BIOS Upgrades.
Major BIOS manufacturers include:
• American Megatrends Inc. (AMI)
• Phoenix Technologies
• ALi
• Winbond
As with changes to the CMOS Setup, be careful when upgrading your BIOS. Make sure you are upgrading to a version that is compatible with your computer system. Otherwise, you could corrupt the BIOS, which means you won’t be able to boot your computer. If in doubt, check with your computer manufacturer to be sure you need to upgrade.
Bootstrap Management
Boot Other Device
Common Options : Enabled, Disabled
Quick Review
This BIOS feature determines whether the BIOS will attempt to load an operating system from the Second Boot Device or Third Boot Device if it fails to load one from the First Boot Device.
This feature is enabled by default and it is recommended that you leave it as such.
Boot Sequence
Common Options : A, C, SCSI
C, A, SCSI
C, CD-ROM, A
CD-ROM, C, A
D, A, SCSI (only when you have at least 2 IDE hard disks)
E,
SCSI (only when you have at least 3 IDE hard disks)
F, A, SCSI (only when you have 4 IDE hard disks)
SCSI, A, C
SCSI, C, A
A, SCSI, C
LS/ZIP, C
Quick Review
This BIOS feature enables you to set the sequence by which the BIOS will search for an operating system during the boot-up process. To ensure the shortest booting time possible, set the hard disk that contains your operating system as the first choice. Normally, this would be drive C for IDE drives but if you are using a SCSI hard disk, then select SCSI.
Some motherboards have an external (not part of the chipset) IDE controller. In such motherboards, the SCSI option is replaced with an EXT option. If you want to boot from an IDE hard disk running off the internal IDE controller, do not set the Boot Sequence to start with EXT. Please note that this feature works in conjunction with the Boot Sequence EXT Means feature.
Boot Sequence EXT Means
Common Options : IDE, SCSI
Quick Review
This BIOS feature determines whether the system boots from an IDE hard disk connected to an external IDE controller or a SCSI hard disk. However, it will only have an effect if the EXT option had been selected in the Boot Sequence feature.
To boot from an IDE hard disk that’s connected to the external IDE controller, you must set this feature to IDE.
In order to boot from a SCSI hard disk, you must set this feature to SCSI.
Boot To OS/2
Common Options : Yes, No
Quick Review
This is similar to the OS Select For DRAM > 64M BIOS feature.
This BIOS feature determines how systems with more than 64MB of memory are managed. A wrong setting can cause problems like erroneous memory detection.
If you are using an older version of the IBM OS/2 operating system, you should select Yes.
If you are using the IBM OS/2 Warp v3.0 or higher operating system, you should select No.
If you are using an older version of the IBM OS/2 operating system but have already installed all the relevant IBM FixPaks, you should select No.
Users of non-OS/2 operating systems (like Microsoft Windows XP) should select the No option.
Boot Up Floppy Seek
Common Options : Enabled, Disabled
Quick Review
This BIOS feature determines whether the BIOS checks for a floppy drive during boot-up or not.
If enabled, the BIOS will attempt to detect and initialize the floppy drive. If it cannot detect one, it will flash an error message. However, the system will still be allowed to continue the boot process.
If this feature is disabled, the BIOS will skip the floppy drive check. This speeds up the booting process by several seconds.
Since a floppy drive check is really pointless, it is recommended that you disable this feature for a faster booting process.
Boot Up NumLock Status
Common Options : On, Off
Quick Review
This BIOS feature sets the input mode of the numeric keypad at boot up.
If you turn this feature on, the BIOS will set the numeric keypad to function in the numeric mode.
If you set it to Off, the numeric keypad will function in the cursor control mode instead.
The numeric keypad’s input mode can be switched to either numeric or cursor control mode and back again at any time after boot up.
The choice of initial keypad input mode is entirely up to your preference.
Delay IDE Initial
Common Options : 0 to 15
Quick Review
Motherboards are capable of booting up much faster these days. Therefore, initialization of IDE devices now take place much earlier. Unfortunately, this also means that some older IDE drives will not be able to spin up in time to be initialized! When this happens, the BIOS will not be able to detect that IDE drive and the drive will not be accessible even though it is actually running just fine.