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    AST RESEARCH, INC.           TECHNICAL BULLETIN # 1438               2-9-96

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    			Ascentia 950N with Desktop Projectors

    This is an informational bulletin.

    External display devices that support only 640x480 resolutions may not be
    compatible in simultaneous display mode with notebook computer systems
    that use SVGA display modes, such as the AST Ascentia 950N series.

    In SimulSCAN, the Cirrus Logic GD7543 video chip has to accommodate the
    more restrictive LCD panel.  Both the CRT and LCD outputs are 800x600.

    For optimum performance, use a higher resolution desktop projector
    (800x600), or a lower resolution (640x480) Ascentia 950N CS10 model.

    NOTE

    The CL-GD7543 chip supports three display modes: panel mode, CRT mode,
    and SimulSCAN (simultaneous display mode).
    The LCD panel acts as a fixed frequency monitor, it only displays 800x600,
    and it does so at a frequency of 53hz or 60hz, depending on the panel type
    (DSTN or TFT).  This is true for both text and graphics modes (text modes on
    standard desktop graphics adapters use a 9x14 pixel character, thus a
    720x350 pixel resolution display, the CL-GD7543 can expand this font to fill
    the 800x600 display), the panel always operates at 800x600.

    In CRT mode, the CL-GD7543 chip operates as a standard SVGA controller,
    in display resolutions from 640x480 to 1024x768, with horizontal frequencies
    up to 75hz.  You should be able to use a variety of output devices from
    display projectors to desktop monitors just as if you were using a desktop
    system.

    In SimulSCAN, the CL-GD7543 has to accommodate LCD panel.  Since the
    CRT and LCD outputs will be the same the CRT must support 800x600 at
    either 53hz or 60hz.  If the CRT cannot support this, then the CRT cannot be
    used with SimulSCAN.

    SYSTEMS AFFECTED
    AST PART NUMBER AND DESCRIPTION

    All Ascentia 950N systems with SVGA display option (800x600 LCD).