[comp.lang.c] writing in CGA video memory

joaquinv@solist.htsa.aha.nl (Joaquinv Villar) (02/09/90)

When writing to the CGA video memory (IBM PC segment 0xb800) by using
the poke(VSEG,OFFSET) funktion the "snow effect" will occur.

Can anyone tell me if this effect also occurs when reading from the 
CGA video memory ? (by using peek(VSEG,OFFSET)).
I can't check this, because my system has a monochrome monitor (hercules).

To avoid the "snow effect" you have to wait for video retrace.
I do have a routine (called vpoke()) wich I now use in some programs.
In case of running the program on a system with CGA, it works fine.
Will it also work without problems on other graphics adapters.
(e.g. EGA or VGA) ?

Please reply directly to : joaquinv@solist.htsa.aha.nl
Thanks.