John Coffman
2015-10-12 06:55:19 UTC
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I am starting a new thread to move the ColorVDU discussions away
from the "SBC-188 respin" heading.<br>
<br>
AFAIK, no one has played with timing other than EGA on the Color VDU
board. The 8563 is spec'd up to a 16Mhz frequency, so correct EGA
oscillator timing is achieved by using 16.257Mhz, which is close
enough to the 8563 upper limit to work.<br>
<br>
Actual CGA timing could be achieved by using a 14.318Mhz
oscillator. Many of the CRTC parameters would have to change to get
to 525 lines interlaced at 15.75Khz horizontal, and 30Hz vertical
refresh. One would want to tap into P26 with a cable to a 9-pin DE9
(female) connector to a CGA monitor.<br>
<br>
--John<br>
<br>
<br>
<br>
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I am starting a new thread to move the ColorVDU discussions away
from the "SBC-188 respin" heading.<br>
<br>
AFAIK, no one has played with timing other than EGA on the Color VDU
board. The 8563 is spec'd up to a 16Mhz frequency, so correct EGA
oscillator timing is achieved by using 16.257Mhz, which is close
enough to the 8563 upper limit to work.<br>
<br>
Actual CGA timing could be achieved by using a 14.318Mhz
oscillator. Many of the CRTC parameters would have to change to get
to 525 lines interlaced at 15.75Khz horizontal, and 30Hz vertical
refresh. One would want to tap into P26 with a cable to a 9-pin DE9
(female) connector to a CGA monitor.<br>
<br>
--John<br>
<br>
<br>
<br>
</body>
</html>
<p></p>
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