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Date:      Sat, 19 Apr 1997 14:13:14 -0400
From:      Randall Hopper <rhh@ct.picker.com>
To:        multimedia@freebsd.org
Cc:        Amancio Hasty <hasty@rah.star-gate.com>
Subject:   bt848/fxtv: More info on system freezes
Message-ID:  <19970419141314.20369@ct.picker.com>

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     I beat on the system freeze problem this morning, and whittled it down
to a very simple procedure that always quickly reproduces the problem on my
system.

     First, how to reproduce it, followed by my system configuration:

HOW TO REPRODUCE

     1) Start up X with no clients except a single stock xterm.
     2) Start up fxtv 0.4 such that it doesn't overlap the xterm.
        fxtv is continuous displaying to the screen w/ direct video.
     3) Now, start up a full-screen app (a text-mode app; runs in the xterm)
     4) Lean on the key that causes the app to redraw its display

     After about 10-30 seconds, the xterm font gets corrupted.  Shortly
     thereafter (milliseconds or seconds later), the X server locks up
     hard.  Display dead, keyboard dead, mouse dead.

     Sometimes if I'm quick about it, I can get up off the "refresh" key in
     time for the queued refreshes to quit "after" the font is first
     corrupted but "before" the X server has locked.  I can then
     Ctrl-Alt-Bksp to kill the server, and start it up again, giving me a
     sensible display with no traces of the corruption.

     Seems to be evidence that the X server state is being corrupted 
     somehow, and not the system in general.

     Further evidence that this is typically localized to the X server and
     its state is that, if I have a kernel rebuild going on in an xterm and
     the the lock-up occurs, the kernel build will continue for 30-60 sec,
     presumably until the ptty device queue fills up because there's no
     process on the other end slirping off of it.

     Also of note is that after the font corruption starts, it continues to
     mutate some with each refresh.  Line corruption through characters is
     the most common and stays fairly constant across refreshes, but there
     is some "white noise" (stray pixels) that appear and disappear in the
     font characters.  Also, the corruption is in the colors that are used
     on the xterm at the time (purple, white, and blue).  Seems to indicate
     that the font data is being corrupted before it's being blasted on the
     screen rather than after the fact by some corruption directly applied
     to the frame buffer.

SYSTEM CONFIGURATION

     Motherboard:  ASUS P55TP4XE (Triton 1), P100, 32Meg mem
     Video Card :  STB Velocity 3D (S3988 "Virge", 4Meg VRAM)

     FreeBSD Ver:  2.2-GAMMA
     XServer Cfg:  XFree 3.2A (S3V server)
                   1024x768 555 16bpp w/ 1152x900 desktop

     XTerm Cfg  :  stock xterm; 80x47 geometry w/ 9x15 font

     TV Software:  Driver - bt848-970401 w/ Amancio's "missing fields" patch
                   Client - FXTV 0.4

     BIOS Cfg   :  I did try Steve's suggestion of:

                   PCI Streaming = OFF; Video BIOS Cache = OFF; 
                   VGA Palette Snoop = OFF

                   All testing done/problems encountered this morning were
                   with these settings.


Randall



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