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bios disassembly
#1
hi, i'm trying to dissassemble my old P3 mainboard bios for understanding the compatibility issue with a modern graphics card. I'm using IDA disassembler. Can someone tell me what I/O port EB refers to and also help me understand the purpose of the assembly instructions (start of bootblock) given below?

seg001:E45C mov al, 0BDh ;
seg001:E45E mov ah, al
seg001:E460 out 70h, al ; CMOS Memory:
seg001:E460 ;
seg001:E462 out 0EBh, al
seg001:E464 mov al, 55h ;
seg001:E466 out 71h, al ; CMOS Memory:
seg001:E466 ;
seg001:E468 xchg ah, al
seg001:E46A out 70h, al ; CMOS Memory:
find
quote
#2
hi,
i have identified one probable cause of the incompatibility though not 100% sure. my motherboard(award ver 6.00) bios is not properly identifying device BAR's if it is a combination of 'Prefetchable' type and '64 bit decoder' while pci enumeration. i have checked motherboard bios(award/phoenix) upto year 2004 and still found the same coding. am i correct in assuming that all the graphics cards manufactured upto 2004 were not having any BAR's in 64 bit memory space? Can i get a confirmation from someone in this regard so that i can mod by bios?.

thanks,
g.gandhi


(05-02-2013, 01:41 AM)gandhig Wrote: hi, i'm trying to dissassemble my old P3 mainboard bios for understanding the compatibility issue with a modern graphics card. I'm using IDA disassembler. Can someone tell me what I/O port EB refers to and also help me understand the purpose of the assembly instructions (start of bootblock) given below?

seg001:E45C mov al, 0BDh ;
seg001:E45E mov ah, al
seg001:E460 out 70h, al ; CMOS Memory:
seg001:E460 ;
seg001:E462 out 0EBh, al
seg001:E464 mov al, 55h ;
seg001:E466 out 71h, al ; CMOS Memory:
seg001:E466 ;
seg001:E468 xchg ah, al
seg001:E46A out 70h, al ; CMOS Memory:
find
quote
#3
hi, i'm really happy to share that at last the modern graphics card got detected by my old motherboard bios after i modded it to introduce a delay and a patch for proper handling of 64 bit prefetchable memory request by a pci device in the awardext.rom module.
find
quote


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