3.4.4 CLOCK CONSIDERATIONS
A major design element of the WD9500-SET1 is the provision for two
separate and independent clock rates; one for drawing operations, the
other for screen refresh. In particular, faster monitors can be used
without changing the clock rate of the drawing facilities within the WD9500-SET1, and conversely, use of slower monitors will not degrade
drawing speed.
The system clock signal, provided by an external 60MHz oscillator,
drives the drawing process within the WD9500-SET1 , and is used to
generated VRAM timing. The pixel clock, used to drive the screen refresh process, is selected from among eight oscillator outputs to accommodate different types of monitors. Three PDM output signals, CLKSEL2, CLKSEL
1, and CLKSELO, are provided to make the selection.
In the United States, non-interlaced video monitors use a vertical
refresh frequency of 60Hz; in Europe, the standard is 70Hz. Including
the interlaced IBM 8514 monitor (vertical frequency 43.48Hz) produces
Table 14, in which the "Pixel Frequency" is the frequency of the
oscillator selected by CLKSEL2, CLKSEL 1, and CLKSELO as input to the
PDM's PCLK pin.
The typical WD9500-SET1 board will therefore be configured with
oscillators at 25.28, 44.90 and 64.37MHz for use with U.S. standard
monitors, or with oscillators at 31.40, 44.90, and 74.16MHz for use with European standard monitors. A more ambitious design might include all
seven clock frequencies, with the MID2-MIDO inputs (as per
"Configuration Strapping" earlier in this chapter) aiding in the selection.
Louis Ohland wrote:
https://www.ardent-tool.com/video/WD_9510_MC.html
Alex wrote:
Did anyone in the group buy the PARADISE 8514/A PLUS CARD? I am after the
@adf. Have the same card but no @adf in ardent database
https://www.ebay.com/itm/146445369444?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=l3cB-wWCSoW&sssrc=4429486&ssuid=LFC-JFTBRDe&var=&widget_ver=artemis&media=COPY
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