[comp.sys.amiga] Screen Death

waterman@cory.Berkeley.EDU (T.S. Alan Waterman) (10/15/87)

     Regarding this talk about multiple screens dying all over in a big way:

  About a month ago, I ran into a great display bug (feature ?-). I was running
everything in non-overscan screens. Interlaced workbench, interlaced DBW VT100
(v2.2 -- anything higher tends do do nasty things to my system--haven't
bothered to track it down yet), and two show (Fish disk 72 ??) screens, one
full-blown HAM, the other sixteen color interlaced.

  Flipping through these, with the mouse and a little help from A-N and A-M,
I got a display with the top half being the top half of the HAM picture,
only it had the colors from the other show picture. This is where things
start to get strange: the bottom half had EIGHT replicas, in miniature, of
the hi-res picture, with the WORKBENCH colors!!

   Flipping up to another screen, it went away; so, I chased it. With the
two show screens as the highest, sliding one down across the other would
send the display into random hysterics, with little miniature images in
the wrong colors everywhere. Once it went into that near_death syndrome
called fireworks_display_mode in the manuals. 

  Alright, so this is wierd, yeah, but who cares? Well, the thing is, try
as I might, the machine would not crash from this. It was (is) infinitely
repeatable, but it _never_ crashes the machine!  Anybody have any clues?

   I wonder whether it's an Intuition bug that can happen even if you
do everything `right', or if it's something peculiar (very) to Show.
Anyone seen it quite like this?



--T.S.
=======the Truth, the (w)hole Truth, and nothing but the Truth======
=======I don't really care who's opinions these are.  Do you? ======

ali@rocky.STANFORD.EDU (Ali Ozer) (10/15/87)

In article <4374@zen.berkeley.edu> T.S. Alan Waterman writes:
>    [Talking about multiple screens dying]
> ...  Alright, so this is wierd, yeah, but who cares? Well, the thing is, try
>as I might, the machine would not crash from this. It was (is) infinitely
>repeatable, but it _never_ crashes the machine!  Anybody have any clues?
>   I wonder whether it's an Intuition bug that can happen even if you
>do everything `right', or if it's something peculiar (very) to Show.

Well, at least the "minimal" form of the bug (which Tom mentioned
in an earlier msg: interlaced WB + interlaced screen + non interlaced screen +
front-to-back + front-to-back => FIREWORKS) seems to be a system problem,
and can crash the machine if you play with the mouse (instead of using 
A-N/A-M). Tom and I tried it on a second Amiga (512K, as opposed to Tom's
1.75M), and sure enough, same results. We tried the same thing with various 
other programs that open custom screens, such as Viewilbm (not Show), TeX 
previewer, Fed, and same results all the time. Then I tried it on a 2.5M
machine, and once again, same results. 

So the programs aren't to blame, probably Intuition is... Seems like when
you depth arrange screens of different view-modes the copper list fails to
get assembled correctly (maybe?). (In all our tests the colors of the messed
up screen seemed right --- Usually the view modes and the bit maps were
screwed up.)

Ali Ozer, ali@rocky.stanford.edu

ali@rocky.STANFORD.EDU (Ali Ozer) (10/15/87)

[]
One more observation: From an interlaced WB, open up as many 
interlaced TeX Previews as you want. Things are fine --- You can front-to-back
to your heart's content, no fireworks. But then simply "uninterlace" one
of the preview screens (TeX previewer is so nice it lets you switch between
non-interlaced and interlaced screen on the fly), front-to-back to WB,
and front-to-back to an interlaced preview, and BLAM! The system can handle
many interlaced screens, so the fact that it can't handle 2 interlaced
and one not seems to be a silly bug (Dale? Jim?) rather than some 
SYSTEM LIMITATION. (Imagine the TV ads: You can open upto ONE noninterlaced 
and TWO interlaced screens at once! 6 simultaneous tasks! 4 windows on
desktop! 40 directories per volume! Amiga, the machine with the unreachable
limits!) [Aren't we glad this is not the case. 8-) ]

Ali Ozer, ali@rocky.stanford.edu