[comp.os.minix] ega bug

richard@ucf-cs.ucf.edu (02/02/90)

I have Minix 1.2 running on a 386 with a VGA monitor. Periodically, my
screen will go black from some line of the output down.  When this line
of the output scrolls off the screen, the lines below it reappear.  

I have heard rumors of an "EGA bug."  Does anyone remember far back enough
to tell me if this is that bug, and what the fix is?

Richard Dunn-Roberts                  richard@ist1.ucf-cs.ucf.edu

ast@cs.vu.nl (Andy Tanenbaum) (02/05/90)

In article <12500002@ucf-cs.ucf.edu> richard@ucf-cs.ucf.edu writes:
>I have heard rumors of an "EGA bug."  Does anyone remember far back enough
>to tell me if this is that bug, and what the fix is?

The problem is that EGA video RAM does not wrap around the way the IBM PC
video RAM does.  Thus EGA is not IBM compatible. :-(

The fix is to do all the scrolling in software.  Starting with 1.3, this
feature was standard.  You hit the F3 hit to enable it.  It is slower, but
it works.  The fix is moderately complicated, and involves a lot of
assembly code.

Andy Tanenbaum (ast@cs.vu.nl)