OpenEuphoria

Re: Mode 18 memory access

• Posted by "Cuny, David" <ATB.DCUNY at HW1.CAHWNET.GOV> Mar 19, 1997
• 1039 views

Peter Blue wrote:

> To read data from each plane set port #3CE = 4 and set port #3CF to the
> plane number (ie 0 for plane 0, 1 for plane 1, 2 for plane 2, 3 for plane
> 3) and PEEK the data.

Thanks for the help. Moving bitmaps in memory (as opposed to sequences) is
blindingly fast, even on my 386. Using the built-in Euphoria routines made
me wonder if I could ever get the code running fast enough to be useful.

> You can write to 1,2,3 or 4 planes at the same time by setting port #3C4 =
> 2 and setting the appropriate bits in port #3C5 (ie BIT 0=1 for plane 0,
> BIT 1=1 for plane 1, BIT 2=1 for plane 2, etc ...) and POKE in your data,
> don't forget the screen base address is #A0000 (NOT #A000 as in DOS)

I see that I can write all 4 planes at once, but can I read them at once as
well?

The code I wrote allocates four seperate buffers (actually, four contigious
buffers) for each of the planes, and reads them in. Writing is the reverse.

If I could read all 4 planes at once, I'm assuming that I could use 1/4 the
memory, and I could write them out faster.

Thanks again!

 -- David Cuny