From: "Andrej Brodnik (Andy)" Newsgroups: comp.os.msdos.djgpp Subject: __dpmi_physical_address_mapping Date: Fri, 11 Oct 1996 18:09:05 +0200 Organization: Lulea University Lines: 29 Message-ID: <325E7121.167EB0E7@sm.luth.se> NNTP-Posting-Host: my21.sm.luth.se Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit To: djgpp AT delorie DOT com DJ-Gateway: from newsgroup comp.os.msdos.djgpp We are building a PC board which occupies 256kB of address space. It'l be put somewhere above 1M and inside 24-bit address space. Now, the SW will be running under (for testing purposes -- yeap it's a research) DOS. We are using djgpp C compiler and we think to use procedure __dpmi_physical_address_mapping to access the board. I have a couple of questions answers on which I'd appreciate a lot. 1) Does somebody has a piece of code using the above procedure? If yes, can we get it? (not the whole programme, only the piece which uses the procedure. 2) How "expensive" is to access the memory this way? How many instructions? 3) How complicated is to put the whole programme (we are under DOS) in the protected mode at the beginning and then (is possible) access the memory directly? What does such an attempt mean from the point of view of (re)coding of the existing programme (we are using gcc now). Thanx in advance a lot for your answers! Andrej PS: If you have an answer on one, few or all questions, please do not hesitate to send it/them. I will appreciate all of them greatly.