| Composite video output from ST [message #283087] |
Thu, 20 March 1986 15:06  |
jpexg
Messages: 3
Registered: September 1985
Karma: 0
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Article-I.D.: mit-herm.2587
Posted: Thu Mar 20 15:06:13 1986
Date-Received: Sat, 22-Mar-86 23:20:53 EST
Distribution: net
Organization: The MIT AI Lab, Cambridge, MA
Lines: 12
The 1040ST, and now the 520ST, offer composite video output compatible with
normal monitors, or rf-modulated for TVs. There were a few questions here
a while back about how the ST reads its video memory to drive the display
without slowing down the processor (answer--video reads are done while the
processor isn't using the bus, mostly) but now Atari has come out with an
additional video output, which can't be compatible with the "normal"
display drive as that is 70Hz, non-interlaced and regular monitors are
60Hz, interlaced. Does the new 60Hz display use the same technique as
before, using the bus alernately with the processor, so all three of them
are banging away? This makes it seem like there would be frequent bus-
contention, especially between the 60Hz and 70Hz accesses. Is there some
kind of magic that makes this less of a problem?
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| Re: Composite video output from ST [message #283100 is a reply to message #283087] |
Sat, 22 March 1986 17:44  |
jpexg
Messages: 3
Registered: September 1985
Karma: 0
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Junior Member |
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<pre>
Article-I.D.: mit-herm.2588
Posted: Sat Mar 22 17:44:16 1986
Date-Received: Tue, 25-Mar-86 04:12:48 EST
References: <2587@mit-hermes.ARPA>
Distribution: net
Organization: The MIT AI Lab, Cambridge, MA
Lines: 6
Since noone has answered my question yet, here it is for anyone who's
interested (the question was how do the new ST's generate 60Hz and 70Hz
video simultaneously):
In fact they don't. The 70Hz monitor, if used, is detected and causes the
ST to generate the appropriate video signals. Otherwise 60 Hz (only) is
generated, at least I think this is what happens.
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