Mail Archives: djgpp/1999/01/29/08:55:07
Hi all,
How are ya all? hope u r all perfectly okay!
Here are some questions!! :-)
1) what is _djgpp_conventional_base? there is a mention of it in the FAQ
but i dunno what it is! is there any explanation of it in the help
files? which file? i couldn't find any explanation for it anywhere!!
perhaps because i dunno how to search well! :-(
and here is a simple paradox...
(please correct me if i am wrong in any point here! I am not really 100%
sure of what i am writing!)
the 386 has some models of operation. of which i am only interested in
two, the segmented model, and the flat model. I have understood that the
flat model is the same as the segmented but with all segments set to the
same values (i.e. they all point to the same descriptor). they all begin
at 0 and span 4gb, right?
Now...
a) is there any kind of protection when using the flat mode? how comes?
all the memory is available and i can write to anywhere without causing
an exception!
b) I assume djgpp runs in flat model! right? this is copied from faq...
>Programs compiled with DJGPP can access all the physical memory on your
>machine and support virtual memory. All this memory presents a flat
address
>space with no segmentation (you can say goodbye to far and huge
pointers
>and to memory models), and is only limited by the amount of virtual
memory
>supported by the DPMI server in use.
great... now all the memory is available! why do i get a SIGSEGV fault
when i executed a very simple CLS function?
mov edi,0xa0000
mov ecx,16000
mov eax,0
rep stosd
I am puzzled!
3) where can i find info about pages, page table... etc... i have read
intel reference, but i couldn't understand any thing!! :-(
looking forward to hearing from u soon... ;-)!
with lots of luv,
Mohamed El Dawy
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