Mapping Video BIOS?

[Greg 'groggy' Lehey]

On Sunday, 27 July 2003 at 22:32:42 -0600, M. Warner Losh wrote:
> In message: <20030728043155.GV45069 at wantadilla.lemis.com>
>             "Greg 'groggy' Lehey" <grog at FreeBSD.org> writes:
>> On Sunday, 27 July 2003 at 22:17:32 -0600, M. Warner Losh wrote:
>>> In message: <20030728041557.GU45069 at wantadilla.lemis.com>
>>>             "Greg 'groggy' Lehey" <grog at freebsd.org> writes:
>>>> On Sunday, 27 July 2003 at 22:11:29 -0600, M. Warner Losh wrote:
>>>>> Where are you getting the data?  A windows tool?
>>>>
>>>> If you're talking about the BIOS contents I'm printing, yes, I'm using
>>>> a Microsoft tool called DEBUG (which has been around since before
>>>> Microsoft bought DOS :-).
>>>
>>> I don't suppose that you could use FreeBSD's /dev/mem + od?
>>
>> Yup, can do.
>>
>>> dd if=/dev/mem bs=64k skip=12 count=1 | hd | less
>>
>>   00000000  55 aa 78 e9 44 06 00 00  00 00 00 00 00 00 00 00  |U.x.D...........|
>>   00000010  00 00 00 00 00 00 00 00  68 01 00 00 00 00 49 42  |........h.....IB|
>>   ...
>>   0000bff0  04 03 80 00 0c 00 00 00  20 00 10 0b 3e 00 02 40  |........ ...>..@|
>>   0000c000  ff ff ff ff ff ff ff ff  ff ff ff ff ff ff ff ff  |................|
>>   *
>>   00010000
>>
>> That's pretty much what I expected.  Up to offset bff0, it's identical
>> with the Microsoft dump.
>
> Shouldn't you be looking at 0x000c0000 instead of 0x0000c000?

Yes, I am.  Look at the calculations in the dd above: skip 12 blocks
of 64 kB, or 0xc0000.  If you mean the output of Microsoft's DEBUG,
that's in 8086 real mode, segment:offset.  The segment registers are
logically shifted 4 bits to the left, so C000:0000 is 0xc0000.

Greg
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