Understanding your BIOS

Discussion in 'Hardware' started by TYCOON, Jun 27, 2005.



    Jun 27, 2005
    My effort to explain what the setting in your BIOS do.
    Examples in "Olive" are based on my current rig.
    Processor: 2400+ (unlocked) w/SP-97
    Motherboard: NF7-S Rev.2
    RAM: Generic Samsung 2x512 Pc3200(400MHz)
    Video Card: Radeon 9800Pro
    //CPU MENU//
    CPU Operating SpeedUser Defined
    This option lets you select the actual operating speed "2400+" or "user defined" which allows you to change External Clock and Multiplier Factor.
    External Clock205
    This setting controls the clock speed of the memory bus on the motherboard. The internal processor speed is the product of the "External Clock" x "Multiplier Factor" = 2537MHz
    Multiplier Factor11.5
    This setting controls the multiplier that is used to determine the "Actual clock speed" of the processor relative to the external or motherboard clock speed. "External Clock" x "Multiplier Factor" = 2537MHz
    CPU FSB/DRAM ratio3/3
    How your RAM interacts with your "External clock"
    External Clock = 200MHz
    Divider 3/3
    RAM = 200MHz(400MHz Effective)
    External Clock = 133MHz
    Divider 4/6
    RAM = 200MHz(400MHz Effective)
    CPU Interfaceenabled
    This setting just increases the FSB speed, however it's pointless as you should already have the option to set the FSB to whatever you want. (Googled not sure if true)
    CPU Core voltage or Vcore2.03
    This setting controls the amount of voltage going into your cpu. Note that you shouldn't raise this too high unless your cooling is up to the task as it CAN damage your CPU.
    DDR SDRAM Voltage2.9
    This setting controls the amount of voltage going into your RAM.
    Chipset Voltage1.7
    This allows you to change the "chipset voltage" or the "northbridge" (nForce 2 Ultra 400) this usually allows you to get higher overclocks.
    AGP Voltage1.5
    This is the voltage going into your video card, raising this will do nothing to help you obtain higher overclocks. And may damage your card. Unless otherwise posted, keep this at 1.5 as the extra power is drawn from the "external molex connector" (9800Pro).
    //AGP Menu//
    Init Display FirstAGP
    This BIOS feature allows you to select whether to boot the system using the AGP graphics card or the PCI graphics card.
    AGP Aperature Size128MB
    This is when you run out of Video RAM, it then allocates RAM from the windows 4 GB memory address space. As far as I know this is pointless with AGP cards but is usefull with integreted graphics cards.(may be rong in this)
    AGP Frequency66MHz
    This should be kept at 66MHz to keep from frying your video card. But even very small changes cause severe system errors, destabilization etc.
    AGP Data Transfer Rate8x
    The Accelerated Graphics Port operates at a clock speed of 66 MHz, but allows for a variety of high transfer rates, depending on the specific mode of operation. AGP currently allows for transfer rates of 1x, 2x, 3x, 4x, or 8x. Any newer AGP card should be set 8x if the BIOS doesnt automatically do it. Older cards will operate at a 4x interface.
    AGP Fast Write Capabilityenabled
    Fast Write allows the AGP device act like a PCI device. This allows it to bypass the main memory and directly access the data which improves AGP read performance. However AGP write performance is not affected. You should turn this on.
    //BIOS MENU//
    System BIOS Cacheabledisabled
    On most systems, you can shadow your system BIOS ROM. Caching of the motherboard BIOS ROM from F0000h to FFFFFh by the processor's Level 2 cache. This greatly speeds up accesses to the BIOS. This
    is a waste of the Level 2 cache's bandwidth. I recomend to disabled it.
    Video RAM Cacheabledisabled
    This like the "System BIOS Cacheable" will use the processor's L2 cache. With the VIdeo RAM to cache that small 64KB region of the video RAM. The performance of the graphics card will most probably receive a boost from the lower latency and higher bandwidth of the processor's L2 cache. Again this is a waste of the Level 2 cache's bandwidth. I recomend to disabled it.
    FSB/AGP Spread Spectrumdisabled
    This option is to eneable modulating of the signal it generates so that the spikes are reduced to flatter curves. Usually offers two levels of modulation - 0.5% or 1.0%. System stability may be compromised and I recommend that you disable this feature.
    Quick Power on Seld Test/ Quick Boot
    Enabling this setting will cause the BIOS power-on self test routine to skip some of its tests during bootup. One of the key things this setting usually does when enabled is cause the POST to skip checking all of extended memory for errors.
    Boot up Floppy Seekdisabled
    This BIOS feature determines whether the BIOS checks for a floppy drive during boot-up or not.
    Security OptionSetup
    The ability to have the BIOS password protected.
    CPU Thermal throttlingdisabled
    CPU Throttling occurs when the CPU becomes 'too hot'. The CPU throttles down the load to decrease it's core temperature. The default setting is usually 62.5%or 50.0%.I turn this off as I know my cooling is fine.
    CPU Disconnect Functiondisabled
    A far as I know this drops the CPU temperature during idle time and possibly lowers the energy used but I don't recommend it because it may make the system unstable when overclocked. If you have good cooling don't use it
    Memory Timing Settings
    The memory's real speed is determined by the timing that the system is told to use, often via settings in the BIOS setup program. These settings control how quickly the system will try to read or write to the memory.
    CAS (Column Access Strobe)
    A signal which tells the DRAM to accept an address as the column address. Used in conjunction with Row Access Strobe (see RAS) to select a bit of DRAM.
    CAS Latency
    CAS latency refers to the ratio between column access time and clock cycle time. Since column access time refers to the period after the CPU requests a column, to when the data is moved to the output line, a lower CAS latency means less clock cycles to move the data to the output line. It is usually recommended you use the lowest CAS latency which your RAM and motherboard can run stable with.
    Tras (Active to Precharge)
    Tras specifies the amount of time required between an active command to a precharge command. Basically this means the number of cycles that must pass after a bank is opened to when it can be closed. It is usually recommended you use the lowest Tras which your RAM and motherboard can run stable with.
    RAS# to CAS#
    This is the delay in memory cycles between the time a row is activated and when a column of data within the row can actually be requested.
    RAS Precharge
    This is the time in memory cycles that is required to flush an active row out before a new row can be requested. This only comes into play when a request is made to an inactive row.
    Anyhoo, hope this helps.
    TYCOON, Jun 27, 2005
    1. Advertisements



    Jun 26, 2005
    Thats really nicely made! Some bios's are a bit different but mostly they all have the same stuff thee. At least all basic thing and then companies add their own things in that are unique.
    stlava, Jun 27, 2005
    1. Advertisements



    Jun 21, 2005
    i just look at the bios to know what the hell i am to do... to bad i can't code my own... otherwise it would PWN :D
    unholy, Jun 27, 2005


    Jun 26, 2005
    Very informative Tycoon great job. I nevedr did understand all those RAS and CAS thingys.
    werty316, Jun 28, 2005


    Jun 21, 2005
    yes... theres alot more in there... i love to make my ram run fast!!!!
    unholy, Jun 28, 2005


    Jun 26, 2005
    If you really want to learn more about BIOS and its optimization you should refer to the BOG (BIOS Optimization Guide) at ARP forums: www.rojakpot.com
    zachig, Jun 28, 2005


    Jun 21, 2005
    or u could go for the good old trial and error (not suggested!!!)
    unholy, Jun 29, 2005
    1. Advertisements

Want to reply to this thread or ask your own question?

It takes just 2 minutes to sign up (and it's free!). Just click the sign up button to choose a username and then you can ask your own questions on the forum.
Similar Threads
  1. Evil Uncle Chris

    Confirm my wireless understanding please?

    Evil Uncle Chris, May 1, 2005, in forum: Wireless Networking
    Sooner Al [MVP]
    May 1, 2005
  2. Ghazan Haider

    Understanding voice AIMs

    Ghazan Haider, Nov 28, 2004, in forum: Cisco
    Doug McIntyre
    Nov 28, 2004
  3. AM
    May 26, 2005
  4. Daniel Farley
  5. Pennywise@DerryMaine.Gov

    BIOS question - how to unlock a bios

    Pennywise@DerryMaine.Gov, Jan 11, 2010, in forum: Computer Support