On 5/2/05, Viktor Pracht <[EMAIL PROTECTED]> wrote: > Am Sonntag, den 01.05.2005, 13:06 -0400 schrieb Timothy Miller: > > > Interesting approach #1: Periodically, scan the VGA data and > > translate/scale it to another buffer that is read by the video > > contoller. > > > > Interesting approach #2: Catch writes to VGA memory and convert them > > immediately. > > #1 won't work because each write to memory of a real VGA chip goes > through a 5-stage pipeline, with various logical operations performed at > each stage. One of the operations involves the value latched during the > last read, which means reading is not trivial either. > We absolutely need #2. We can add a second (even smaller) nanocontroller > to do #1 if it turns out that drawing a character on every write and/or > refreshing the whole screen after mode changes takes too long. How long > is a memory access and an I/O access allowed to take?
You're ALLOWED to take a very long time. There's a PCI transaction called a target disconnect without data, and you can keep doing that indefinitely. I think before we continue talking about the controller logic, we need to have a complete description of what a normal VGA device needs to implement and how it all works. _______________________________________________ Open-graphics mailing list [email protected] http://lists.duskglow.com/mailman/listinfo/open-graphics List service provided by Duskglow Consulting, LLC (www.duskglow.com)
