    AST RESEARCH, INC.        TECHNICAL BULLETIN # 1401          7-12-96

    TITLE: Ascentia External Monitor Flicker

    SUMMARY

       An external monitor, connected to an Ascentia 950N or an Ascentia P
       system through the external video port, may experience noticeable
       flicker.

       This issue applies to all the Ascentia 950N and Ascentia P systems.

    ISSUE

       When an external monitor is attached to the external video port on
       the Ascentia system in simultaneous video mode, there may be
       noticeable flicker on the monitor.  When the unit is set for
       external video mode, the monitor image appears to be flicker-free.

    BACKGROUND

       If the unit is configured to operate in simultaneous video mode,
       the VGA controller in the Ascentia system must generate
       signals that are compatible with the internal display panel.
       If the Ascentia has a Dual Scan STN display, the external
       video will be 800 x 600, with a vertical refresh rate of 53 Hz.
       If the Ascentia is equipped with a TFT display, the external
       video will be 800 x 600 with a vertical refresh rate of 60 Hz.

       Screen flicker will usually result on a CRT-based monitor with
       vertical refresh frequencies of 53 and 60 Hz.  The LCD panels used
       in  portable computers operate much differently than CRT devices,
       and therefore do not exhibit any type of flicker at the lower
       refresh rates they require.

    ACTION

       If the external monitor flicker is excessive, set the unit to
       operate in external video mode only.  When operated in external
       video mode, the video controller circuitry in the Ascentia
       functions the same way as a standard SVGA controller, with vertical
       refresh rates of up to 75 Hz., depending on video mode and driver
       support.

    NOTES

       N/A

    TAN 009323RH and 001226JP

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