Re: Another idea for outputting to VGA/DVI/HDMI

[Eric J <ejumzguy@gmail.com>]

>
> >> Video sync is a solvable problem. Either take the signal where it is
> >> available (IIe slot 7, etc.) or write a program that will allow the VGA
> >> card/software to sync.
>
> > True. Maybe even write a signature to the beginning of the video memory
> > and sync to it. Once in sync it should stay in sync till a reset, so the
> > signature doesn't need to stay there longer than a few milliseconds.
>
> > -Alex.
>
> I would prefer a method that doesn't require interfering with the
> operation of the Apple.
>
> I also don't understand why it would necessarily stay in sync.  Is it
> safe to assume that the Apple's crystal and the Carte Blanche crystal
> are so close to the same frequency that they would not drift out of sync
> in a noticeable amount of time?

You would not want to use the CB's on-board clock. Instead, you would
want
to utilize the FPGA's DCM (digital clock manager, usable as a
frequency
multiplier) to derive your operating clock based on the A2's own 14M.
In this case, you would indeed stay in sync.