My opinion: Definitely built onto the board. As simple as possible, without sacrificing the 2nd screen. No speed optimizations, unless they reduce work.
Back in the 1990s, I did a paper exercise of splitting the QL circuit diagram into a modular board system. With separate boards for CPU, Video, I/O ports connected by a powered back plane.
The idea was to develop different boards to to enhance the system.
Maybe a separate video board for the Issue 8 board would introduce a little flexibilty to have a dedicated QL video card.
On board or separate, it would still be possible to have an external video card on the expansion bus later, and that video board would probably work in an Issue 6 or 7 QL too. In Issue 5, IO would be interesting and probably require a bit of extra logic to be plugged into the 8301 socket.
The idea of having an 8301 based video on a daughter-board on ISS8 is there so that it can be replaced by a CPLD based card that would do _STANDARD_ QL video with VGA compatible timing - because we are running out of QL compatible vintage displays. IT's not intended as an expansion, just a way to keep the QL in it's vintage form when no vintage displays are available.
Cristian wrote:To be specific, would it be possible to replace the RF out with a standard VGA port?
Obviously keeping the QL standard 512x256 @ 4 (or 8) colors.
You'd have to create a scan doubler. Given that VGA is getting rare now you might as well go the whole hog and create an HDMI output. You could probably build a stripped down version of the OSSC, which is open source so all the circuit diagrams etc. are available, and incorporate that into a daughter board.
Well, I mentioned VGA simply because they were talking about "video with VGA compatible timing". I'm open to other solutions (DVI, HDMI etc..).
On the other hand, it's not so difficult to find a cheap VGA monitor. Furthermore, several people might want to emulate the experience of the original "QL Vision Monitor" utilizing a CRT monitor.