From: Shawn Hargreaves Newsgroups: comp.os.msdos.djgpp Subject: Re: memcpy after djgpp nearptr enable//VESA 2.0 double buffer problem Date: Mon, 30 Jun 1997 21:17:56 +0100 Organization: None Distribution: world Message-ID: References: <33B7DA72 DOT DDF8E94E AT mwci DOT net> NNTP-Posting-Host: talula.demon.co.uk MIME-Version: 1.0 Lines: 20 To: djgpp AT delorie DOT com DJ-Gateway: from newsgroup comp.os.msdos.djgpp Precedence: bulk Larry Swanson writes: >I'm kind of embarassed to admit this, but I'm having trouble getting a >double buffer working. ... >* In the above code "video" is the address of the linear frame buffer >obtained from VESA 2.0 plus *__djgpp_conventional_base. The address you get back from the VESA driver is a physical, hardware memory location, while your djgpp code is using virtualised protected mode addressing. The nearptr hack lets you access memory outside your data segment, but you still need to map the physical address range into your linear address space, with the __dpmi_physical_address_mapping() function. There's some example code to do this on http://www.rt66.com/~brennan/djgpp, or you might want to look at the vesa.c and dpmi.c files from Allegro... -- Shawn Hargreaves - shawn AT talula DOT demon DOT co DOT uk - http://www.talula.demon.co.uk/ Beauty is a French phonetic corruption of a short cloth neck ornament.