Need more ideas for retrieving BIOS code from flash chip

Gin

I am trying like to get a copy of the BIOS code off the BIOS flash chip, modify it, and restore it. My goal is to change a single operation in the assembly code that runs during the BIOS boot process.

When the computer boots it displays the following BIOS information:
PheonixBIOS 4.0 Release 6.0
Copyright...
All rights....
Copyright 1996-2000 Intel Corporation
4S4EB2X0.10A.P09

Dell Dimension XPS T750r
BIOS Version A08
Intel Pentium(R) III processor 750 MHz

I contacted Dell, the computer manufacturer, and have access to the current version (A08) of the BIOS code but unfortunately it is bundled into the upgrade utility in a single .exe file so I am not able to get at the BIOS binary file.

I've also tried the free-ware utility from the Internet, UniFlash, which allowed me to get the BIOS binary file from the BIOS. However, it seems that the BIOS file has problems - I cannot match the instructions in the BIOS file with the assembly instructions. In fact the file doesn't even have any bootup strings... makes me assume the file has a special format or did not copy off correctly(???). (By-the-way, I DO find the assembly instructions when I use the DOS utility MSD and look directly into the BIOS-mapped memory space, starting at F0000, so I know its in there somewhere.) I also retreived 3 Option ROM binary files from the PC using UniFlash but they also do not appear to contain the code that I'm looking for.

Does anyone have any suggestions?

p.s. the chip is soldered onto the board so I can't pop it out and use an EEPROM programmer.

p.s.2. I'm very new to the world of BIOSes so please do not assume that I know any more than what I've written above. I've had input from people I work with and this is the extent of what we know to check for.

Thanks very much for any new ideas that you can send down the pike!

- Ginny

Rainbow · Posted: Sat Jul 20, 2002 10:52 am Post subject:

BIOS image is compressed in the Flash ROM. The only part that can be disassembled is the bootblock at the end of the image.

BTW.: That board looks to be OEM version of intel SE440BX-2 board http://www.intel.com/support/motherboards/desktop/se440bx2/
_________________
Patched and tested BIOSes are at http://wims.rainbow-software.org
UniFlash - Flash anything anywhere http://www.uniflash.org

pfelgate · Posted: Thu Oct 10, 2002 9:47 pm Post subject:

Is there any way therefore to change the boot block to overwrite the necessary memory location in RAM before the RAM copy is executed?

Alternatively, does anyone know the compression format of the BIOS? If sourcer can read it, someone must know how it's compressed.

Rainbow · Posted: Thu Oct 10, 2002 10:22 pm Post subject:

Phoenix BIOS is not good BIOS for experiments because there are almost no programs and also no documentation. My favourite is Award BIOS which uses standard LZH compression to compress the blocks into single image, with simple bootblock at the end (which can initialize ISA VGA card and boot from floppy).
_________________
Patched and tested BIOSes are at http://wims.rainbow-software.org
UniFlash - Flash anything anywhere http://www.uniflash.org

MMAMUK · Posted: Tue Jul 13, 2004 7:48 pm Post subject:

Have a look at the following URL for editing the Phoenix BIOS:

http://www.wimsbios.com/phpBB2/viewtopic.php?t=2294