Re: How does the apple2 RGB card work?

["Bryan Parkoff" <none@nospam.net>]

"General_Failure" <tristan.mumford@gmail.com> wrote in message 
1148636626.941077.84200@u72g2000cwu.googlegroups.com">news:1148636626.941077.84200@u72g2000cwu.googlegroups.com...
> Hello.
> I'm feeling a little disappointed after losing an ebay auction for an
> apple2 RGB card to snipers.
>
> So, in my usual spirit, If I can't get something at a decent price I
> make my own.
>
> Are there any schematics in existence for an RGB card?
>
> If not, can someone enlighten me on how it gets hold of the necessary
> video data?
>
> If I can find out enough, I'll probably build one on one of those
> wonderful 8-bit babies.
>
> Another If. If it is as simple as listening to the bus for certain
> memory writes to track the mode and the screen data, I can see a nice
> cached card with a VGA frequency horizontal refresh being relatively
> easy. Relatively.
> Of course, TTL levels would be a lot easier. Small steps and all that.
>
Hello,

    I am sorry to hear since you lost eBay auction.  It is an offical Apple 
//e's 80 Col / RGB card what you are referring.  I am not aware if it has 
only RGB card existence for Apple II+.  There is no schematic existence.  It 
is very rare to find.
    It is only the way to draw schematic in your own by looking at 8-bit 80 
Col / RGB card because it is much simpler and less complex.
    KnutRoll-Lund has succeeded building an adapter from DB-15 (80 Col / RGB 
card) to DB-9 (CGA) for any CGA monitors because AppleColor M100 monitor is 
rare to find.  The 16 wrong colors do not look identical to Apple II colors, 
but it is only acceptable what we have now.  Knut used GAL16V8 chip to swap 
some out of 16 colors to almost match Apple II color.
    Right now, he and I are working together to develop schematic.  After 
the schematic is developed, he may be able to design aux controller card for 
VGA monitor, but it is almost impossible to deal between 15.734K and 30K 
horizontial freq.  DMA may be needed.
    For couple weeks, I have been working using Oscilloscope to capture 
video binary from Apple //e's 80 Col / RGB card and Apple IIgs' RGB.  I will 
let all of folks know when 4,096 possibilities of data in a table for video 
binary is complete.

Bryan Parkoff