CMOS commands

STANDARD CMOS

Date and Time
definition: Allows user to set date and time
options: Any date and time the user feels like setting
results: None really, unless the user is stupid

IDE Channel settings/HDD Disk C type
definition: Hard Disk C type refers to the number of the system's primary (master) hard drive. The default number is 47, which specify that the user must enter the drive specifications according to the HDD manual.
options: Cyln (# of cylinders), Heads (# of heads), WPcom (Write precompensation, useless in modern computers), LZone (same as Wpcom), Sect (# of sectors per track), Size (Calculated from # of heads, cylinders, and sectors)
results: Allows user to set hard drive manufacturer specifications about the hard drive to be installed in the system.

Floppy Drive settings
definition: Allows setting configuration of floppy drives A: and B:
options: 1.44 MB (3½” floppy) 2.88 MB (3½” floppy) or 1.2 (5¼” floppy).
results: Allow user to set floppy drive manufacturer specifications about the floppy drive to be installed in the system.

Primary Display
definition: Set type of display standard being used, and in the case of two video adapters, the primary one.
options: VGA/PGA/EGA, black/white, Mono, Hercules, MDA
results: Depending on the type of video adapter or monitor being used, the above setting should be set in accordance with manufacturers specifications.

Halt on (post error displays)
definition: User defines if the computer will display an error message if it encounters problems with the boot sequence.
options: Enable/Disable
results: If enabled, the computer will display an error message

ADVANCED SMOST SETP/BIOS FEATURES

Above 1 MB Memory Test
definition: Allow the user to set whether the system will check the memory above 1 MB for errors.
options: Enable/Disable
results: Typically disabled for faster boot. Test also conducted in HIMEM.SYS driver for DOS 6.0 with XMS (Extended Memory Specification).

Memory parity error check
definition: Enabling this feature will allow the system to test for bit errors in the memory. Every byte will contain an extra bit to make the parity even or odd.
options: Enable/Disable
results: If the memory fails the test then an error message will appear stating there is a RAM failure. Most modern memory chips are of such high quality as to make this setting obsolete.

System Boot sequence
definition: Enables user to set the order of the drives in which the BIOS will search for an operating system.
options: A, C, SCSI/EXT
C, A, SCSI/EXT
C, CD-ROM, A
CD-ROM, C, A
D, A, SCSI/EXT (only when you have at least 2 IDE hard disks)
E, A, SCSI/EXT (only when you have at least 3 IDE hard disks)
F, A, SCSI (only when you have 4 IDE hard disks)\
SCSI/EXT, A, C
SCSI/EXT, C, A
A, SCSI/EXT, C
LS/ZIP,C
results: Each variation defines the order in which the BIOS will search for an OS.

Swap Floppy Drive
definition: This option allows the user to switch the logical arrangement of the floppy drives without opening the case.
options: Enable/Disable
results: Enable switches the mapped access to the two floppy drives in the system

Boot up Floppy Seek
definition: Allows the user to set whether the BIOS searches for a floppy in the boot process.
options: Enable/Disable
results: Enable searches for floppy, error message if not identified, detect number of tracks (40 or 80)

Boot up system speed (fast boot up)
definition: This specifies the processor speed that the system will boot from.
options: High, Low
results: The HIGH setting is recommended for a faster boot process. If problems occur during the boot process the use the low setting.

External/Internal Cache
definition: Define whether the L2 cache is external or internal, often in two different menu items.
options: Enable/Disable
results: Depending on location of L2 cache on motherboard or chip, this setting will define that.

BIOS/SYSTEM/VIDEO ROM Shadowing
definition: Allows the user to set whether Shadowing will be used to accelerate the BIOS read process.
options: Enable/Disable
results: BIOS are copied to the system RAM for quicker access. Improves the BIOS performance as it is read through a 64-bit DRAM bus as opposed to an 8-bit XT bus.

CHIPSET FEATURES/ADVANCED CHIPSET SETUP

AT Bus Clock Selection
definition: Gives a division of the CPU clock (System Clock) so it can reach the ISA-EISA bus clock.
options: CLK/x, (or CLKIN/x and CLK2/x) CLK refers to the processor speed and x is an integer value like 2, 3, 4, 5, etc.
results: This setting is for data exchange with ISA cards. The setting must be just right, too high or too low will adversely affect system performance.

Memory Read Wait State
definition: Determines how long the memory controller should wait before sending the read data to the data requester (CPU, peripherals, etc.)
options: 0 Cycle, 1 Cycle
results: The 0 Cycle option provides optimal performance but may cause system instabilities. The 1 Cycle option causes the memory controller to wait one cycle before sending data. This is the default.

Memory Write Wait State
definition: This Determines how long the memory controller should wait before sending the write data to the requester.)
options: 0 Cycle, 1 Cycle
results: The 0 Cycle option provides optimal performance but may cause system instabilities. The 1 Cycle option causes the memory controller to wait one cycle before sending data. This is the default.

Cache Read Option
definition: Referred to as SRAM Read wait state or Cache Read Hit Burst. Sets the specification of the number of clocks needed to load four 32-bit words into a CPU internal cache. Clocks per word.
options: 2-1-1-1 (5 clocks to load 4 words), 3-1-1-1 (6 clocks), 3-2-2-2, 4-1-1-1, other simple integer values…
results: The lower the computer can support the better.

IDE Multi Block Mode (IDE Block Mode)
definition: This setting enables IDE drives to transfer several sectors of data per interrupt depending on the setting.
options: Mode 0 (Standard mode transferring a single sector at a time), Mode 1 (no interrupts), Mode 2 (sectors are transferred in a single burst, Mode 3 (32-bit instructions with speeds up to 11.1 MBps, Mode 4 (up to 16.7 MBps), Mode 5 (up to 20 MBps)
results: The more sectors transferred per interrupt will increase the Hard drive speed in respect to reading and writing data. Setting the too high can cause errors with the Com, serial, ports, etc.

DRAM lead off timing/Refresh Rate
definition: This option allows the user to adjust the time needed before the data written to DRAM can be accessed and DRAM refresh intervals.
options: 3,4 for Leadoff timing; 7.8 µsec, 15.6 µsec, 31.2 µsec, 64 µsec, 128 µsec for refresh rate.
results: Set leadoff timing to 3 for faster access to DRAM or to 4 if there are system stability issues to be dealt with. The refresh rate determines the amount of rows and order in which the memory will refresh. Increasing the interval will increase performance unless taken to the extreme.

System BIOS Cacheable
definition: Enables a user to speed access to the BIOS, which may not be necessary as the OS does not really need to access the system BIOS very much.
options: Enable/Disable
results: Speeds access to the system BIOS by caching the system BIOS ROM at F0000h-FFFFFh

PCI Passive Release/PCI Delayed Transaction
definition: Allows the user to define whether the chipset’s embedded 32-bit write buffer to support delayed transaction cycles
options: Enable/Disable
results: Enabling this allows the chipset's embedded 32-bit write buffer to support delayed transaction cycles This frees the PCI bus up to perform other duties while it is processing the ISA transaction, which is buffered. This is because ISA is much slower than PCI. It is recommended to keep this option Enabled.

PLUG and PLAY/PCI or PNP/PCI CONFIG

Latency Timer (PCI Clocks)
definition: Allows control of the length of time each PCI device controls access of the bus before the next.
options: 0 - 255
results: The larger the value, the longer the PCI device can keep control of the bus, which improves bandwidth. Conversely, other PCI devices must wait until they have access.

Slot X Using INT#
definition: Selects an INT# channel for a PCI Slot.
options: A, B, C, D, Auto
results: #A is allocated automatically. Extra channels are assigned as necessitated by the card.

Xth available IRQ
definition: Allows selection or map of IRQ for one of the available INT#s. 1st available
options: 3, 4, 5, 6, 7, 9, 10, 11, 12, 14, 15, 1st available, NA
results: 1st available will select the first open IRQ, NA means the IRQ is assigned to the ISA bus and not available to PCI.

PCI IDE IRQ Map Items
definition: Allows configuration to specify the type of IDE disk controller and the type of slot being used. You can also specify the INT#s for each drive.
options: PCI-Auto, PCI Slot X, Primary IDE INT#, Secondary IDE INT#, ISA
results: Auto assigns appropriate INT# channel to IRQ 14, Slot X allows user to input slot number, IDE INT# assigns two INT channels if supported for primary and secondary, ISA assigns no IRQ to PCI.

AT Bus Clock Frequency
definition: AT bus speed in a PCI system
options: 6 – 8.33 MHz
results: Set depending on speed of PCI bus

PCI Clock Frequency
definition: PCI bus speed in a PCI system
options: ## MHz
results: Set depending on speed of PCI bus

ISA Bus Clock Frequency
definition: ISA bus speed in a PCI system
options: 6 – 8.33 MHz
results: Set depending on speed of PCI bus

INTEGRATED PERIPHERALS/ADVANCED

Peripheral Configuration
definition: This sets the method by which the system receives the legacy card information.
options: Use ICU, Use Setup Utility
results: the Use ICU option if there is a P-n-P BIOS that can automatically detect and configure the system I/O devices. The Use Setup Utility option lets the user provide the system setup information to the BIOS by using setup utility software. If there is P-n-P, then its use is recommended.

Floppy Options
definition: Allows setting configuration of floppy drives A: and B:
options: 1.44 MB (3½” floppy) 2.88 MB (3½” floppy) or 1.2 (5¼” floppy).
results: Allow user to set floppy drive manufacturer specifications about the floppy drive to be installed in the system.

Video Configuration
definition: Set type of display standard being used, and in the case of two video adapters, the primary one.
options: CGA/VGA/PGA/EGA, black/white, Mono, Hercules, MDA
results: Depending on the type of video adapter or monitor being used, the above setting should be set in accordance with manufacturers specifications.

HDD Block Mode
definition: Block mode enables data to be sent from multiple sectors at once instead of the previous single sector method. This greatly speeds up hard disk access. If disabled then only 512 bytes of data can be sent per interrupt which would slow down the system. This option should be enabled, but use caution with Windows NT because of problems with data corruption.
options: Enable/Disable
results: The BIOS will automatically detect if your hard disk supports block transfers and configure the proper block transfer settings for it. Up to 64KB of data can be transferred per interrupt.

IDE Settings: PIO/UDMA
definition: Allows the user to set the Programmed Input/Output or Ultra DMA mode for the master and slave devices.
options: 0, 1, 2, 3, 4, Auto
results: Auto allows BIOS auto detection. Over clocking may result in a loss of data.

USB Keyboard/Latency Time
definition: Enables and disables support for USB keyboards
options: Enable/Disable
results: Enable if using USB keyboard , disable otherwise

POWER MANAGEMENT

Enable/Disable
definition: Enables power management utilities and options
options: Enable/Disable
results: Enable turns on options

Doze
definition: Amount of time before the system will reduce 80% of activity.
options: specify amount of time
results: Amount specified defines amount of idle time before the system reduces activity.

Standby (Stby)
definition: Amount of time before the system will reduce 92% of activity.
options: specify amount of time
results: Amount specified defines amount of idle time before the system reduces activity.

Suspend
definition: Amount of time after the system goes in the most inactive state possible, which is 99%. After this state, the system will require a warm up period so the CPU, hard disk and monitor may go online.
options: specify amount of time
results: Amount specified defines amount of idle time before the system reduces activity.

Power Button Override
definition: Allows user to decide how to boot the machine.
options: Button Only, Keyboard 98, Hot Key, Mouse Left, Mouse Right
results: Setting defines what button must be pressed to boot the machine.

SECURITY

Password-Supervisory/User
definition: Set a password that will be requested upon boot.
options: No password/Disabled (Default), Enabled
results: Improves security by giving the supervisor control over who accesses the system and their privileges (Read-Only, Read-Write, etc.) while they are using the system.

REFERENCES
Adrian's Rojak Pot; www.itcp.net/~awsh/
The BIOS survival Guide; http://burks.bton.ac.uk/burks/pcinfo...sg/bios_sg.htm
Upgrading and Repairing PCs; Scott Mueller with Craig Zacker; 13th edition, Que Corporation; ISBM 0-7897-2542-8

for me there no need to make huge changes in ur cmos. just use the default. still working. just set the boot and ide detecting. but very good work bro. must put much effort on in. very useful to most of us

Amazing tutorial! Greenies to you.

An extremely good tutorial on a subject I knew very little about ;) Definitely worth greenies and a " Make another tutorial!" -- Jason Copeland

Good tut !
The mem write wait states always confused me :)
So once again thanks
Regards
Mike

Great tutorial. You have my vote.

Well.... do you have any idea about RAS Delay and CAS Delay. Also "Memory Hole at 15-16M".

RAS: Row Addressing Strobe
CAS: Column Addressing Strobe

Quote:

Originally posted here by Neo
Great tutorial. You have my vote.

Well.... do you have any idea about RAS Delay and CAS Delay. Also "Memory Hole at 15-16M".

RAS: Row Addressing Strobe
CAS: Column Addressing Strobe

Those strobes are the way Memory is addressed by the cpu. The delay is the amount of ticks the cpu waits before sending the data on. The registers in the cpu must be full of said addressed data or errors will occur. The shorter the tick the faster the machine is able to refresh it's internal registers.

I think(not sure) that the 15-16 meg hole defines which address that is using for memory "Paging" a window that is used to address ranges outside the cpu's address bus.

great job

Keep up the good work!