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How to Configure BIOS settings
Published  06/21/2011 | Troubleshooting Computer | Rating:
How to Configure BIOS settings

Using the BIOS setup, you can configure and change the settings of many hardware components. Some of the settings can give you performance boosts if done right. If done wrong, they can cause rapid overheating and can fry your system. While we have tried to keep everything as accurate as possible, it should be noted that the BIOS options in your system may radically differ from what we have described here. Also, we cannot be sure on how these options are implemented in your system.

Make any changes one at a time or in the smallest increments. Test system stability by booting into Windows and working on it for 5 to 10 minutes after each change. If the system becomes unstable, revert to the previous settings. Using these settings is at your own risk!

Memory Options
15M—16M Memory Hole / Memory Hole
Options: Enabled, Disabled
Recommended Setting: Disabled
Explanation: Older ISA cards used the 15th megabyte of memory for their own purposes. Modern EISA, PnP-ISA and PCI cards don’t need this, with one exception: Sound Blaster PCI128 and Sound Blaster Live cards. If you have these cards, leave this enabled.

Autodetect DIMM/PCI Clock
Options: Enabled, Disabled
Recommended Setting: Enabled
Explanation: Turns off unused slots. It may also slightly reduce power usage.


Bank Interleave
Options: Disabled, 2-Way, 4-Way
Recommended Setting: Depends on the memory modules you have.
Explanation: Interleaving requests to different RAM banks can give you a performance boost. 64 MB and lower RAM modules have two banks. Larger modules have four banks. Check your RAM modules and decide.

Data Integrity Mode
Options: ECC, Non-ECC
Recommended Setting: ECC
Explanation: Both the chipset (motherboard) and the RAM have to
support ECC. If you don’t know, then it should be set to Non-ECC.

Delay DRAM Read Latch
Options: Auto, No Delay, 0.5ns, 1.0ns, 1.5ns
Recommended Setting: Depends on the memory modules you have.
Explanation: Tweaks for high RAM loads. Two-sided 256MB modules are high-load, one-sided memory modules are not. For lower RAM loads, set it at No Delay. For high RAM loads, you need to increase the delay. If you are getting crashes after you install new RAM, this is the first place to look.

DRAM CAS Latency Time / DRAM Cycle Length
Options: 2, 2.5, 3
Recommended Setting: Depends on the memory modules you have.
Explanation: CAS latency is part of the wait between the chipset requesting data and the RAM modules getting ready to send it. Shorter delays are better. A lower number is therefore better if your RAM is able to handle it. 2.5 is only available with DDR RAM.

Fast R-W Turnaround
Options: Enabled, Disabled
Recommended Setting: Depends on system stability
Explanation: When the CPU switches from reading to writing there is a delay. Enabling it reduces the delay. Disable it if it causes system instability.

Force 4-Way Interleave
Options: Enable, Disable
Recommended Setting: Disabled
Explanation: This is supposed to force the chipset to use 4-way interleave even if it does not detect it. The chipset will most likely turn on 4-way interleave if it is specified in the Bank Interleaving setting, so you can leave this disabled.

MD Driving Strength/Memory Data Drive
Options: Low, High
Recommended Setting: Depends on the memory modules you have.
Explanation: Change from low to high if the signal strength, under high RAM Load, is insufficient. Changing this setting may affect system stability.

Read Around Write
Options: Enabled, Disabled
Recommended Setting: Enabled
Explanation: Out-of-order read-write commands result in higher performance.

Read Wait State/Read Latency
Options: 0, 1
Recommended Setting: 0 if there is no instability.
Explanation: When a device reads from the RAM, the chipset holds the data for one cycle. Setting it to zero cycles increases performance, but the device may not be ready to receive the data— resulting in instability.

Refresh Interval/Refresh Mode Select
Options: 7.8 μsec, 15.6 μsec, 31.2 μsec, 64 μsec, 128 μsec
Recommended Setting: 128 μsec; depends on the memory modules you have.
Explanation: Every cell in SDRAM and DDR are refreshed every 64 milliseconds. But trying to refresh everything together will result in a power surge which is not good, so it is staggered. 128 MB and smaller modules are refreshed every 15.6 microseconds. 256 MB modules every 7.8 microseconds (μsec). Today’s RAM modules can handle more than the recommended 64 μsec between refreshes. A setting of 128 μsec increases performance and reduces power consumption.

SDRAM Command Leadoff
Options: 3, 4
Recommended Setting: Depends on system stability
Explanation: 3 is better.

SDRAM Idle Limit/SDRAM Idle Timer
Options: Disabled, 0 cycles, 8 cycles, 12 cycles, 16 cycles, 24 cycles, 32 cycles, 48 cycles
Recommended Setting: 12 cycles for less than 512 MB, 32 cycles for all others
Explanation: The idle time before SDRAM recharge. Higher values postpone the recharge and reduce RAM latency. Use this together with the Refresh Interval setting for best results.

SDRAM Precharge Control/SDRAM Page Control
Options: Enabled, Disabled
Recommended Setting: Enabled. Disable it if there is instability.
Explanation: This checks whether the RAM or the chipset should control the refreshing. Enable for RAM to control the refresh. Can cause instability with large amounts of RAM or poor-quality RAM.

Video RAM Cacheable
Options: Enabled, Disabled
Recommended Setting: Disabled
Explanation: Enabling this causes video data to be cached in the L2 cache. Can cause a performance bottleneck when enabled.

PCI and AGP Options
8-bit I/O Recovery Time
Options: N/A, 1, 2, 3, 4, 5, 6, 7, 8
Recommended Setting: N/A
Explanation: Synchronises the PCI-ISA bus. If don’t have an ISA card it does nothing.

16-bit I/O Recovery Time
Options: N/A, 1, 2, 3, 4
Recommended Setting: N/A
Explanation: Same as 8-bit, but for 16-bit transactions. Does nothing without an ISA card.

AGP 2x Mode and AGP 4x Mode
Options: Enabled, Disabled
Recommended Setting: Enabled
Explanation: This enables or disables AGP 2x or 4x depending on what your BIOS shows. Even if your card is AGP 2x and you set it to 4x, the chipset will fall back to 2x, so there is no harm in enabling this setting.

AGP Aperture
Options: Disabled, 8MB, 16MB, 32MB, 64MB, 128MB, 256MB
Recommended Setting: Disabled
Explanation: Controls how much system RAM the AGP card is allowed to use for AGP texturing. If you’re not a heavy gamer, and if you don’t work too much with 3D applications, there’s no point assigning an AGP aperture. Also, if you’ve got, say, only 256 MB of RAM, you don’t have RAM to spare—hence the AGP Aperture should be disabled.

Assign IRQ to PCI/AGP VGA
Options: Enabled, Disabled
Recommended Setting: Enabled
Explanation: Tells the BIOS to assign an IRQ to the display. Useful for Windows 95/98/ME. Makes no difference to Windows 2000/XP if enabled.

CPU to PCI Write Buffer
Options: Enabled, Disabled
Recommended Setting: Enabled
Explanation: Sets the priority to the CPU when writing to the PCI bus. Better performance if enabled. May cause instability with some sound cards.

Fast Writes
Options: Enabled, Disabled
Recommended Setting: Disabled
Explanation: There’s a very slight performance increase if enabled. But it causes instability with video cards that doesn’t support Fast Writes.

I/O Recovery Time
Options: Enabled, Disabled
Recommended Setting: Disabled
Explanation: Enable this if you are facing problems with any ISA cards you may have.

Master Priority Rotation
Options: 1 PCI, 2 PCI, 3 PCI
Recommended Setting: Depends on your configuration.
Explanation: Controls CPU access to the PCI bus. If you have RAID and SCSI, 3 PCI is better. With NICs and TV-Tuners, 1 PCI is better. You will have to experiment for your configuration.

Passive Release
Options: Enabled, Disabled
Recommended Setting: Depends on how your system responds.
Explanation: Allows ISA devices to write to the Passive Release Buffer without waiting for the PCI bus. Enable for better performance; disable if your ISA cards or NICs have problems.

PCI #2 Access #1 Retry
Options: Enabled, Disabled
Recommended Setting: Enabled
Explanation: Works with the CPU to PCI Write Buffer. Enabling this will tell the buffer to retry any writes to the bus. Disable it if you face performance issues and your PCI bus has high-bandwidth devices. Many retries will jam the bus.

PCI Delay Transaction/PCI 2.1 Compatible/PCI 2.1 Compliance
Options: Enabled, Disabled
Recommended Setting: Enabled
Explanation: A buffer between the faster PCI and the slower ISA. If enabled, may cause problems with some sounds cards. Look for driver updates for the cards.

PCI Dynamic Bursting
Options: Enabled, Disabled
Recommended Setting: Enabled
Explanation: PCI devices write to this burst buffer, and the buffer writes to the PCI bus when it is free or the buffer is full.

PCI Latency
Options: 16 to 255
Recommended Setting: It varies. It’s usually set to 32 or 64.
Explanation: This controls the time a PCI device is allowed to use the bus.

PCI Master 0 WS Write
Options: Enabled, Disabled
Recommended Setting: Enabled
Explanation: Disabling puts a 30ns write delay for PCI busmasters. Disable this if you are facing issues with SCSI or a NIC.

PCI Master Read Caching
Options: Enabled, Disabled
Recommended Setting: Disabled
Explanation: Caches PCI Master reads to the CPU’s L2 cache. Will cause a performance hit on the CPU if enabled.

PCI Master Pipeline Req/PCI Pipelining
Options: Enabled, Disabled
Recommended Setting: Disabled
Explanation: Enable for better performance with a PCI video card, TV-Tuner, etc. May cause system instability with some devices when enabled.

Sidebanding
Options: Enabled, Disabled
Recommended Setting: Enabled
Explanation: Enabled is faster. Permits AGP to send addresses down different lines to data.

Other options
Force ESCD update
Options: Enabled, Disabled
Recommended Setting: Enabled
Explanation: This refreshes the ESCD (Extended System Configuration Data) data on every boot, regardless of whether it’s changed or not.

IDE Access mode
Options: CHS, LBA, Large/Other
Recommended Setting: Depends on your hard disk.
Explanation: CHS for drives smaller than 512 MB. LBA for drives that are larger. “Other” or “Large” for drives that do not support LBA after 8 GB, usually very old drives that are larger than 8 GB.

PnP Aware OS
Options: Enabled, Disabled
Recommended Setting: Depends on the OS
Explanation: Enable for Windows 95, 98, NT4 and ME, and Linux kernels without ACPI support. Disable for Windows 2000 and XP.

USB Legacy/BIOS USB Keyboard/BIOS USB Translation/USB
Keyboard Support
Options: Enabled, Disabled
Recommended Setting: Disabled
Explanation: Allows a USB keyboard to work in Win 3.x, MS-DOS, and other environments that are not USB-aware. Enable only if you need to use an USB keyboard in a DOS environment, for example, flashing your BIOS from a DOS boot disk.

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