From:	eplmst AT lu DOT erisoft DOT se (Martin Stromberg)
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: Accessing SMBIOS memory above 1 MB
Date:	17 Dec 2002 08:57:45 GMT
Organization:	Ericsson Erisoft AB, Sweden
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References:	<BLEIKKOJPIJGGPFINPJHIEFGCAAA DOT nharwood AT bigpond DOT com>
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To:	djgpp AT delorie DOT com
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Nigel Harwood (nharwood AT bigpond DOT com) wrote:
: I wrote a program to return useful information from a systems SMBIOS under
: Windows NT and this works for computers that have this memory mapped below
: 1MB but silently fails on the first _farpeekb() when this memory is mapped
: above 1 MB.

: I am running the program under Windows NT 4.0.

: As far I know I am doing these accesses correctly as have always worked fine
: for other computer models.  I've re-read the FAQ and can't see anything else
: to consider.  I've scanned the web but found nothing relevant.  I've
: searched the mailing list archive and found one similar question but no
: answer.

: I'm hoping that this mailing list will provide the answer.

: The approach I am using is:

:    unsigned char c;
:    unsigned short smbios_selector;
:    __dpmi_meminfo meminfo;

:    meminfo.size = smbios_entry_point.structure_table_length;
:    meminfo.address = smbios_entry_point.structure_table_address;  // address
: is 0xFEEF800

:    __dpmi_physical_address_mapping(&meminfo);
:    smbios_selector = __dpmi_allocate_ldt_descriptors(1);
:    __dpmi_set_segment_base_address(smbios_selector,meminfo.address);
:    __dpmi_set_segment_limit(smbios_selector,meminfo.size-1);

:     c = _farpeekb(smbios_selector,0);  // first byte of SMBIOS memory

: Using debug statements I can confirm that the program fails at the
: _farpeekb().  Absolutely no error message appears it just comes back to the
: command prompt.

Does it work if you run plain DOZE? (You can get a DOS from
<http://www.freedos.org> if you don't have it.)

If so then it sounds like NT is blocking access to memory that high.


Right,

						MartinS

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