Can I use a larger capacity bios chip than the original that came with my motherboard

Discussion in 'BIOS Mods' started by kittendoggie, May 5, 2012.

  1. kittendoggie

    kittendoggie MDL Novice

    Apr 21, 2012
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    Hello community

    I have a question that has been puzzling me for sometime:

    What would happen if you buy a larger-size chip, flash it with an EEprom flasher with the bios of a motherboard that comes with a stock bios chip of lower capacity? Would that work?


    Let me speak with an example: the Asus p8p67 pro comes with a 4MB (or 32Mbit) bios chip from factory; what would happen if I take my p8z68-v pro bios chip which is 8MB (or 64Mbit) and flash it externally with the latest p8p67 pro bios. Would my p8p67 pro mobo work? Or would it fry?

    Kind regards.
     
  2. LatinMcG

    LatinMcG Bios Borker

    Feb 27, 2011
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    what i know is.. if its similar chip type and voltage.. only size change, then it should work.

    look for the spec sheet of both .. it shows voltage
     
  3. kittendoggie

    kittendoggie MDL Novice

    Apr 21, 2012
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    Interesting! Thanks.
     
  4. Gelip

    Gelip MDL Novice

    Feb 28, 2011
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    Can anyone confirm this? Has anyone tried to replace original chip to bigger capacity? Is the result of this operation motherboard and PC work no problem?
     
  5. LatinMcG

    LatinMcG Bios Borker

    Feb 27, 2011
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    what subchip is going to validate total size ?
    youre at root of hardware in post... it will read from 0 to end of bios.

    only issue i see is flashing new bios it might not be able to identify chip.. other than that, yes
     
  6. Galileo Figaro

    Galileo Figaro MDL Junior Member

    Sep 6, 2010
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    It will work, provided that:

    -The bigger capacity chip is of the same series (manufacturer) as the original. This is important mainly when you want to flash that chip. The flashers are made for a certain range of chips. If you flash it somewhere else than in the motherboard, then this is no issue, but why would you do that?

    -You need to tie the excess address line to either high or low. Meaning you will feed it either +5V or GND. If you don't it may fluctuate and become like Schrödingers cat, sometimes HI, sometimes LO, sometimes both. You can turn this into a feature if you want. By connecting the highest address line to a switch, you could hand-switch between the lower and higher half of the chip, meaning you could house two versions of the BIOS in the same chip. If you like trying out different modifications to the BIOS you could have one safe version and one experimental.
     
  7. Gelip

    Gelip MDL Novice

    Feb 28, 2011
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  8. osmoTR

    osmoTR MDL Novice

    May 3, 2009
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    #8 osmoTR, Dec 15, 2013
    Last edited by a moderator: Apr 20, 2017
    Asus p8p67 pro of bios those chips are identified and I think only you can use one of them

    Code:
    SST 25LF040.....SST 25LF080.....ATMEL 26DF041/25DF041...ATMEL 26DF081/25DF081...ATMEL 26DF321/25DF321...ATMEL 26DF641/25DF641...ATMEL 26DF161/25DQ161...STM/Numonyx 25PE Series.Intel/Numonyx 25F160/320........PMC 25LV/LQ Series......Micron/Numonyx 25Q Series.......AMIC 25L/LQ Series......GigaDevice 25Q Series...Winbond 25X/Q Series....STM/Micron/Numonyx 25PF/PX Series.......AMIC 25L Series.EON 25F/Q Series........FIDELIX 25Q Series......Spansion 25FL Series....Spansion 25FL(P) Series.EON 25P Series..STM/Micron/Numonyx 25P Series...MXIC 25L Series.ESMT 25L T Series.......ESMT 25L B Series.......SST 25VF Series.ST M29W160B/T...SST 39VF1681/1682.......MXIC 29LV640B/T.Numonyx 28F640/128/256P30B/T....Spansion S29GL128/256/512/01GP
     
  9. Galileo Figaro

    Galileo Figaro MDL Junior Member

    Sep 6, 2010
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    You're right in a general sense, but I'd go the safe route and stick to something the flasher will recognize. The Coreboot flasher is a Linux one that will recognize many different chips. But most people will likely opt for flashing with the original DOS or Windows program.

    The original poster hasn't mentioned whether he (or she) merely wants to use the higher capacity chip in place of the original, and just ignore the excess capacity, or if he wants to in fact make use of the excess capacity. That would be interesting.
     
  10. CodeRush

    CodeRush MDL Member

    Jun 20, 2011
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    #11 CodeRush, Jan 20, 2014
    Last edited by a moderator: Apr 20, 2017
    It can be used but BIOS itself must be modified too. It's Intel-based board, so BIOS image must be altered in many places:
    1. FirstChipDensity value in component section of the descriptor, there are possible values:
    Code:
    #define FLASH_DENSITY_512KB   0x00
    #define FLASH_DENSITY_1MB     0x01
    #define FLASH_DENSITY_2MB     0x02
    #define FLASH_DENSITY_4MB     0x03
    #define FLASH_DENSITY_8MB     0x04
    #define FLASH_DENSITY_16MB    0x05
    2. New chip must be added to VSCC table in the descriptor to enable normal operation for ME code.
    Both 1 and 2 can be edited using Intel FITC 8.xx.

    3. Boot firmware volume must be moved to the end of new BIOS space, so the last byte of Volume Top File (the last FFS file in BFV) will also be the last byte of new BIOS space.
    It can be done with any HexEditor.

    4. All uncompressed PEI files in BFV must be rebased to their new locations to maintain executable-in-place constraint.
    It can be done with UEFITool or MMTool.

    Every BIOS update must be threaten the same way, so my answer for the topic starter: it's possible, but pointless, too much work for nothing.
     
  11. Gelip

    Gelip MDL Novice

    Feb 28, 2011
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    Yes you are right in the case of BIOSes known manufacturers like Award, AMI, Phoenix etc. but the situation is different in the case of coreboot bios to which we have all the source code :)
    ROM_size.png