Re: Let's pay a developer to make a VGA output card

[Mark McDougall <markm@vl.com.au>]

Michael J. Mahon wrote:

> That is the 14MHz "dot clock" I was referring to.  And since each
> video output "state" lasts an integral number of 14MHz periods,
> sampling at 14MHz *exactly* captures all the information in the Apple
> II video.

Ah, OK, I thought you were referring to a (conceptual) 'pixel' clock - 
that makes more sense!

> The shift register value can directly index RGB color values to be 
> output.  I'd guess that 4-5 bits per color would be more than enough 
> resolution.

Yup!

> This may be a conceptual approach with practical problems, requiring 
> a video palette RAM that can be cycled at 14MHz to drive the RGB
> DACs.

No problem inside an FPGA! ;)

> Ah.  I was thinking more of an AUX slot RAM/RGB card with VGA output.
>  Just trying to keep it simple...

As I said, there are other reasons, but you raise an interesting 
possibility to have such an option on my card as well with an 
appropriate connection to the composite output... now I just need to 
know if the 'dot clock' is available on slots other than AUX...

Hmmm... maybe time I did some serious research into this...

Regards,

--
Mark McDougall, Engineer
Virtual Logic Pty Ltd, <http://www.vl.com.au>
21-25 King St, Rockdale, 2216
Ph: +612-9599-3255 Fax: +612-9599-3266