dfoster@jarthur.Claremont.EDU (Derek R. Foster) (11/02/90)
I have some questions regarding the little-known 160x100x16 colors graphics video mode possible on an IBM CGA system. 1) How portable is it? Do you know of any systems that it for certain will/will not work on? 2) What is the most reliable way of invoking it? I have managed to invoke it using some empirically-derived numbers for the video board registers, (I experimented a lot), but I don't know if these numbers are "ideal" or not. (I had to adjust the vertical-hold knob on my monitor slightly to get a clear picture. Perhaps a different set of numbers would make this unnecessary?) Source code in C or assembly would be appreciated here. 3) Is it possible to invoke this mode or a functional work-alike on an EGA or VGA system in its native mode? How? (what values to send to the EGA/VGA registers?) I have written a fairly complex game in this mode, and I am curious just how transportable my game would be to other systems with other video boards, etc. I can make my game run on my EGA board by telling my EGA to simulate a CGA, but when I try to run it on my EGA in native mode, I get either garbage or a working version confined to the upper screen. Evidentally the video timings are different. I would have thought that the greater amount of memory on an EGA board combined with the closer scan lines would mean that I could get more vertical lines of pixels this way, but I can't seem to get it to work. I would appreciate any info that you can give me on this subject. If there is interest, I will post a summary. Thanks in advance! Derek Riippa Foster