Table 3-6. Video Board Ram And Resolution - HP 330 Service Information Manual

Video RAM
Both high- and medium-resolution color video boards have four or six planes of memory. The
medium-resolution board uses eight memory chips per plane. This is enough to display 512
doubled pixels by 400 scan lines. High-resolution boards requires more memory chips per plane.
Resolution is 1024 by 768 single pixels.
Table 3-6 shows how the display RAM is organized for the desired resolution for each board.
Table 3-6. Video Board RAM and Resolution
Video Board
RAM chips Total RAM Resolution
HP 98542 Med-Res Monochrome 8 64 Kbytes 512 by 400
HP 98543 Med-Res Color 32 256 Kbytes
512 by 400
HP 98544 High-Res Monochrome 16 128 Kbytes 1024 by 768
HP 98547 High-Res Color 64 512 Kbytes
1024 by 768
Color Mapping
Color boards have four or six plane color mapping. Mapping is entirely under control of the
Frame Buffer Controller. The high-resolution board has more RAM than the medium-resolution
board.
Display Controller
The Display Controllers are the heart of these video boards. They provide complete video
control and bit-mapped alpha support for one graphics plane. Interfacing directly with the
computer CPU, it integrates and manages most display functions. The functions of the Display
Controllers are:
• Provide horizontal and vertical timing signals to the sweep section of the video board.
• Provide refresh data to the frame buffer.
• Generate the blinking underline cursor.
• Enable window move operations.
• Output video and sync signals to the frame buffers.
Architecture provides for either color or grey-scale monochromatic display use. The display
is organized with one memory byte for each display pixel. This corresponds to a maximum
capability of eight planes with one byte per pixel per plane. Each bit in the byte goes to a
separate frame buffer memory plane. Pixel data is transferred 32 bits (or pixels) at a time by
read and write operations with display RAM by the video board. Logic internal to this chip
enables software to perform byte-per-pixel access.
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Functional Description