okay, got stm32 chip fired up and working :) blinkenlight ftw.
stm32: working interupt based blinker; some nasty lessons learnt, and now trying to work out how fast we can do these in reality.
vsync timing looks more or less correct, so time to put in the line content drawing, the hsync, add the port and DAC back to breadboard and see whaaaas happenin'!
Added vgatest.c variant of moninlink; vsync is in place..