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Thread: VGA BIOS at other than C000 (E000!)

  1. #11
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    Quote Originally Posted by maxtherabbit View Post
    So if I've already edited the IVT, the only other thing that may be hanging me up is the ROM code itself.
    Or a bug in the chipset's ROM shadowing.
    Offering a bounty for:
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  2. #12
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    Quote Originally Posted by maxtherabbit View Post
    I understand that. Being able to run the processor in real mode is important to me
    I guess the question that sort of comes up is if you want the CPU in unencumbered Real Mode and arenít caring about upper memory, etc, does it really matter if the VGA bios shadowing is buggy and the computer still randomly bangs on the non-shadowed copy? Iím not sure what kind of application would really be hitting the BIOS hard enough to materially matter. Itíll affect benchmarks that measure bios/dos text writes, but donít most performance-matters programs just tickle the hardware directly anyway?
    My Retro-computing YouTube Channel (updates... eventually?): Paleozoic PCs

  3. #13

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    No it doesn't matter that much, the system is fine as is. This is just an exercise in curiosity really

  4. #14

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    Thinking about disassembling the video ROM and system BIOS to see what's going on and maybe modify them. What disassembler y'all recommend?

  5. #15

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    Try the free version of IDA 5. After that recent thread about the PS/2 ROM dump, I've used that to disassemble bits of the Model 30-286's VGA BIOS code to answer some of my own questions.

    It may interest you to know that the video stuff (INT 10h) lives in E000 on the non-MCA 286 PS/2s. So AMI's pick of that segment to shadow the video BIOS may not be totally random after all.
    int10h.org :: :: :: blog

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