OpenEuphoria

Re: Graphics mode 257 memory address(es)

• Posted by Roderick Jackson <rjackson at CSIWEB.COM> Apr 05, 1999
• 498 views

>From:  Nick[SMTP:metcalfn at ALPHALINK.COM.AU]
>Sent:  Monday, April 05, 1999 2:43 PM
>
>There is a small virtual screen library for handling higher resolutions with
>the
>program "faster fill" in the (recent?) contributions at RDS's Eu page.  It has
>some functions that you might find useful in the include file vesa.e
>
>Most super vga cards present their memory to the computer through a window
>located
>at #A0000 that is only 64k in size.  When using mode #13 the amount of memory
>needed for a picture is only 320 * 200 = 64000, which fits nicely in one
>window.
>This makes it possible to peek or poke colour values as offsets with ease.
>Graphics modes that use more memory than this can be accessed piecemeal by
>moving
>the 64k window over parts of the video ram.  This can be achieved by calling
>the
>right vesa video interrupt function with the position of the window.  The
>overall
>operation is not trivial however, as the position value is given in granularity
>units, the minimum step possible, and this value varies between cards.

<snip>

Thanks, Nick. That was just what I was looking for. I had
thought there might be an easy, universal, fast method to it.
But it looks like I'll be better off just sticking with mode 19
for what I'm doing. Ah, well... I'll still try out your code
though, since eventually I'll come back to it--and I'll look
into the other packages too, maybe make a higher-resolution
variant for 500MHz+ CPUs. 


Rod Jackson