Asrock ASRFlash Reversing.

Discussion in 'BIOS Mods' started by visions_of_eden, Dec 2, 2010.

  1. visions_of_eden

    visions_of_eden MDL Novice

    Dec 9, 2009

    maybe this argument is a bit old since now XP is almost the the end of its life, but i'm still interested in SLP 1.0 modding.

    Now i'm trying to mod an Asrock k7s41gx bios.

    The problem is that i don't want to touch runtime module to make the mod work , but instead, replace the original DMI information with mine.

    The problem is ASRFlash (asrock flash utility) does not flash the section of ROM in which real DMI data is contained. Opening the bios file with AMIBCP75 reveals the presence of a module #6 "DMI Data" . If you change the content of the module and try to flash it to the bios the process ends succesfully . Dumping the BIOS reveals that the module has been written , but the data reported by DMIScope does not change . This is because real DMI data is not the one contaied in the bios module #6 , but is located at another address, 3A00:0000 in bios image .
    Anything you put in image range 3A00:0000 to 3B00:0000 won't be written to bios chip .

    Now i'm trying to reverse the flasher to understand where this control is made , but it's a hard task , since flasher works on DOS4GW extender , in protected mode.

    I un-binded the protected mode code from DOS4GW runtime and started to analyze with IDA , but did't seem to find any reference to flash commands like address 5555 , 2AAA etc..
    Chip is Winbond W49F002 , so there should be a reference in the code to those values .
    What makes me worry is that the flasher could just use some code directly from the BIOS to flash itself instead of sending its own commands. This way one would have to modify BIOS , then flash patchd bios in turn to write correct DMI data .

    Does anyone who have more experice than me in BIOS re-ing could help me or just point me to the right direction ?

    Thanks .

  2. FreeStyler

    FreeStyler MDL Guru

    Jun 23, 2007
  3. visions_of_eden

    visions_of_eden MDL Novice

    Dec 9, 2009
    Hi !

    DMI tools don't work with this bios. Asrock slightly modified both standard AMI bios and AMI tools . To add DMI string using DMI tools a bios with DMI write function is needed , mine don't have , otherwise i would have added those strings with DMIScope.