Date   : Mon, 02 Mar 2009 23:12:51 +0100
From   : kortink@... (John Kortink)
Subject: New Screen Modes with ARM7 Co-Processor?

On Mon, 02 Mar 2009 20:38:19 +0000 (GMT), Sprow <info@...>
wrote:

>In article <4t9oq4db3acqns9krbins2t4k36l9eq5nj@...>,
>   John Kortink <kortink@...> wrote:
>
>> On Mon, 2 Mar 2009 14:07:59 +0000 (GMT), tommowalker@...
>> wrote:
>> >> I suppose you could put a local CRTC on the copro and do some fun 
>> >> things that way - turn your beeb into some kind of CAD station...
>> >
>> >Some of the later A500 copros had VIDC chips on, I suspect that would
>> >be usable (otherwise why would they have bothered?). 
>
>[snip]
>
>> something like non-interlaced DVI output of the
>> existing modes would be neat.
>
>I thought about something like that a while ago, Chrontel have a number of
>frame buffer -> DVI on-a-chip parts that looked suitable. I forget now why I
>stopped looking, maybe the data needed to be delivered faster than it could
>be sucked out of the beeb's RAM,

The most obvious choice is placing it behind the RGB
output. This gives you a composite sync to unravel and
does not give you the pixel clock. But that is too low
anyway (looking@... Chrontel CH7301 and TI TFP410,
both 25 MHz minimum), and I suppose you can just feed
the RGB and oversample it by using a suitably high,
independent clock.

Another more esoteric one which came to mind is via a
mirror of main memory. E.g. adapter on 6502, put on
fast enough or dual-ported memory maintaining a copy
of main memory, and pull the screen from that as fast
as you like. No teletext though. And probably not much
in the way of support for existing screen trickery,
depending on what you want to invest in emulation.

Or just buy one of those boxes that pretend to connect
your 'retro' apparatus to a modern monitor and hope that
it doesn't tear the signal to shreads ...


John Kortink

-- 

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