I've been thinking about video and sound and keyboard for the 6309 SBC. I put the expansion bus connector on the SBC for this very purpose. A video and sound mezzanine card was in the plans. Of course, at that point, it's no longer an SBC. It's a 2BC or TBC, I suppose. 

I was originally intending to put a TMS9918 or a V9938 device on the card. A small group of us working on the N8VEM Z80 project worked out how to replace the creepy TMS9918 DRAM (ancient 4116 chip with a negative bias rail) with modern SRAM and a few octal latches. So, I know full well that using these vintage video chips is possible. What leaves me cold, however, is that after all that, you're stuck with a composite (NTSC) output. On top of that, the TMS9918 chip in particular is quite power hungry. I really want a nice VGA output with a decent 80 column character mode, maybe 320x240 and 640x480 graphics modes as well. No such beast exists.

On the topic of vintage chips, I'm a big fan of the 6581 SID sound interface device chip. This was the voice of the C64, and the fat sounds that subtractive analog synthesis brings are my preference. This is also possible to interface to the 6309, but with a 3 MHz CPU bus, a lot of glue is required to make it work. The SID is vintage, and scarce, and pricey. It runs hot. Love to have a CMOS one of these that runs with higher bus rates. No such beast exists.

I'm led to the conclusion that one way to satisfy my whims here is to use an FPGA to implement a simple VGA controller, and try out the VHDL SID implementation that I found on the intarwebs. I'll prototype first, of course, because if it doesn't sound good, I'm out. I worry about this, because the FPGA implementation will be via a sigma-delta DAC, rather than the linear DAC and analog filters of a real SID. So, time will tell. 

This is certainly a longer term portion of this project, so I'll not likely have much to say about this for a while. But fun to let anyone reading know what I'm considering, and I certainly welcome the opinions and feedback of anyone who cares to chime in.