CGA & clock speeds

From: Allison J Parent <>
Date: Sun Nov 23 19:01:09 1997

<booted but did not give a display. I could tell it was working by
<DOS commands. I tried then at 5.33 MHz. It booted & ran OK (as far as
<and found that the CGA card depends on the 14.31818 oscilator to run
<Since the processor seemed to be running OK at 8 MHz, what I want to do

Simple make sure you supply 14.31818 to the ISA bus from a seperate
oscillator (or put it on the CGA card and bypass the buss connection).
The problem is that much of the machine is timed off that clock. it is
generated either using then 8284A clock generator or or a TTL oscillator
can. The 8088 is driven off the 8284A (it supplies the correct 33% duty
cycle closk) so it could be done as two seperate sources. There were
"upgrades" that did exactly that yo yeild turbo systems.

Received on Sun Nov 23 1997 - 19:01:09 GMT

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