Re: Memory
Daniel Berstein wrote:
>
> > Hi, anyone can send me a list of memory adresses ?
> > More expecific, I want the starting and ending adresses of video display
> > memory, used to poke and peek in graphics mode 19.
>
> Eduardo, video memory starts at offset #A000 (in hexadecimal), for
> text modes it'a at #B800. You'll have some problems poking directly
> to videomem, mostly related with VGA and SVGA modes... you just can't
> access all the video mem at once, you must swith banks and do some
> other weirds stuff that's better Michael Packard (or Jiri, or
> Jacques, or Ralf) explain.
Careful!!! Euphoria is running in protected mode so offsets must be
32-bit. The video memory for graphics modes is at #A0000, text modes
#B8000. Converting 16-bit segments and offsets to 32-bit ones must be
done by multiplying the segment by 16 then adding the offset.
Mode 19 is the easiest for writing to the screen using pokes. Other
modes require bank-switching as Daniel said and others (16-color) are
set up in bit planes so writes require changing video registers.
Has anyone else noticed that in SVGA modes, graphics operations below a
certain point on the screen are much slower that closer to the top? I'm
guessing that this is from the bank-switching going on. If the software
could detect if each operation would take place in the same bank as was
used last, it could save the time spent calling the bank-switch routine.
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