how do I read a location in the bios eprom

J

just4me

Exactly how do I read a specific location in the bios eprom.
(such as debug.exe location ffff:0000)
 
B

Ben Pfaff

just4me said:
Exactly how do I read a specific location in the bios eprom.
(such as debug.exe location ffff:0000)

Your question is outside the domain of comp.lang.c, which discusses
only the standard C programming language, including the standard C
library. This is a remarkably narrow topic compared to what many
people expect.

For your convenience, the list below contains topics that are not
on-topic for comp.lang.c, and suggests newsgroups for you to explore
if you have questions about these topics. Please do observe proper
netiquette before posting to any of these newsgroups. In particular,
you should read the group's charter and FAQ, if any (FAQs are
available from www.faqs.org and other sources). If those fail to
answer your question then you should browse through at least two weeks
of recent articles to make sure that your question has not already
been answered.

* OS-specific questions, such as how to clear the screen,
access the network, list the files in a directory, or read
"piped" output from a subprocess. These questions should be
directed to OS-specific newsgroups, such as
comp.os.ms-windows.programmer.misc, comp.unix.programmer, or
comp.os.linux.development.apps.

* Compiler-specific questions, such as installation issues and
locations of header files. Ask about these in
compiler-specific newsgroups, such as gnu.gcc.help or
comp.os.ms-windows.programmer.misc. Questions about writing
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* Processor-specific questions, such as questions about
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comp.lang.asm.x86, embedded system processor questions may
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* ABI-specific questions, such as how to interface assembly
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* Algorithms, except questions about C implementations of
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* Making C interoperate with other languages. C has no
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* The C standard, as opposed to standard C. Questions about
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news.groups.questions is a good place to ask about the appropriate
newsgroup for a given topic.
 
B

Ben Pfaff

Your question is still off-topic. Posting it multiple times
doesn't change that.
 
J

jota

Exactly how do I read a specific location in the bios eprom.
(such as debug.exe location ffff:0000)
There is no way of telling!
<OT>
First of all it depends on wheter or not you have an OS,
ok since you have a bios there is almost certenly an OS involved.
But it could be that you are writing the OS your self. Witch you are not!
Anyway! taken that you have an OS, it is an issue for the given OS.
Almost all OSes are executing user apps in something that is called
protected mode or similar to. (Modern ones at least)
In this mode you are effectivly sheilded from most of the tampering with
stuff like reading BIOS locations.
And even if it would be possible, again it could or could not have multiple
address spaces.
And still there is no telling if it could be read!
So thats why you are being denied help here. You are off-topic.
My guess would be that you are running windows, and if thats the case look
for help at
comp.os.ms-windows
</OT>
//jota
 
J

jota

Exactly how do I read a specific location in the bios eprom.
Your question is still off-topic. Posting it multiple times
doesn't change that.
As I see it he was quoting his self!
//jota
 
M

Malcolm

just4me said:
Exactly how do I read a specific location in the bios eprom.
(such as debug.exe location ffff:0000)
In the olden days you could just declare a pointer to an absolute address,
and then read and write to it. This probably won't work anymore, so you will
have to read your compiler documentation to see how to do it. For better
help, try a platform-specific group.
 
D

Dan Pop

In said:
What was your C question?

Are you reading impaired? Even if the answer is that there is no
portable way of doing it, it is a perfectly sensible C question.
Furthermore, the C standard provides a solution, it just doesn't
guarantee that it will work.

Dan
 
D

Dan Pop

In said:
Exactly how do I read a specific location in the bios eprom.
(such as debug.exe location ffff:0000)

First, you have to figure out how to represent this address as a single
integer. After that, you have to convert this integer to the desired
pointer type. Note that modern operating systems, using virtual memory
and memory protection complicate the issue a lot, or may even make a
solution impossible, unless you're running with administrator privileges.

However, in the days of 16-bit MS-DOS, there was nothing between your
code and the raw hardware, so the solution was straightforward:

unsigned char *p = (unsigned char *)0xFFFF0000;

After that, you could use p to access the EPROM bytes. It might still
work in a compatibility 16-bit environment, if compiled as a 16-bit
application on a Windows system (and it will definitely work under MS-DOS
itself). Use a memory model with 32-bit pointers!

The moral is that, although the code itself is as standard C as you can
get, its effect is highly platform, compiler and operating system
dependent.

Dan
 

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