Changing the Pixel Depth

After starting OpenWindows, the window server configures the SX Frame Buffer to support the maximum pixel depth for the screen resolution and frame buffer memory size that you selected. Typically, 32 bits are allocated to each display pixel. But, on the 4-megabyte SX frame buffer, you can increase the screen resolution by choosing a depth of 16 bits per pixel, with some loss of features.

Any frame buffer memory not visible on the monitor display is available to the window server for storing pixmaps. If you want to maximize the amount of off-screen pixmap storage available for your applications, you may need to add the following line to the cg14 frame buffer entry in the /usr/openwin/server/etc/OWconfig file:

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pixelmode="8"

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This forces the window server to initialize the SX Frame Buffer at 16 bits per pixel, regardless of the frame buffer memory size. Table 3-4 summarizes the available features at the 16-bit and 32-bit pixel depths.

Table 3-4 SX Frame Buffer Visuals and Double-buffering

Underlay Visuals	32-bit	16-bit
24-bit TrueColor	Yes	No
8-bit PseudoColor	Yes	Yes
8-bit StaticColor	Yes	Yes
8-bit Greyscale	Yes	Yes
8-bit StaticGrey	Yes	Yes
8-bit TrueColor	Yes	Yes
8-bit DirectColor	Yes	Yes
Overlay Visuals
8-bit PseudoColor	Yes	Yes
Double Buffering
24-bit pixmaps	Software	No
8-bit pixmaps	Hardware	Software
Note: Overlay visuals are limited to 230 colors.