maxtherabbit wrote on 2021-02-23, 15:09:
no one wants some garbage downscaler converting to interlaced, they want native 15kHz progressive scan
separating or combining sync is trivial with a $5 used extron box from ebay
Your thinking of RCA composite not
RGBS component Targa signalling
My Futura 100 portrait system sends a native 512x480 60i
65k color to a 1992 era Magnavox RGBS monitor (a more modern 1080)
The picture is crystal clear albeit interlaced
These screens were designed for hi resolution interlaced video and no scaling is required to send 640x480 to RGBS, the device just drops every other field leaving an untouched clean albeit interlaced image which is what these screens were designed to do anyway.
If we were to build one of these very simple devices he could have protection from blowing up his screen when his video accidentally switches to an unsupported mode.
Starting on a vga monitor , switching to 15khz signaling then switching screens is going to kill any enjoyment of using the screen.
And I wouldn’t trust a home brew rom hack to keep the MCGA adapter in 15khz
If he isn’t worried about desyncing the monitor
His other option would be to use an extron and try to see if the screen has internal trim pots that go far enough to view 320x200 MCGA natively and use dos commands to keep it in 40 column mode on boot.