Steve wrote: ↑Sun Nov 15, 2020 12:11 am
@agranlund Could you explain this automatic internal/external graphics switching in more detail please? Is this something that could be added to the NOVA system provided by Frank Lukas? Cheers
Sure!
On the hardware level it is just a 2-in-1-out VGA switcher IC. I'm using a TS5V522.
The ET4000 and Shifter are connected to this IC and I'm using the spare GPO signal to select which one of these should output to the VGA port.
In my case I also have a UBE-switch clone circuit between the shifter and the TS5V22.
To toggle the output I simply set GPO to either 1 or 0.
(It's bit 6 of YM register 14)
- DSC_0811.JPG (121.06 KiB) Viewed 759 times
I haven't given any thoughts to how you would accomplish this without the mods I already did (remove RF module, make custom board, modify case). I suppose you could probably cut the traces between shifter and monitor port and insert a similar type of circuit between?
Right now I just have a tiny executable in my auto folder that toggles the VGA switch to output the ET4000 after the gfxcard driver has been loaded.
For the next step, to automatically enable ST-Low and shifter when launching a game, I can't give any details yet since I don't actually know until I've done it
The route I'm going to explore is something like this:
- Have a textfile where I can list folders and/or exes that should trigger the autoswitch (I have all my games on F: so in my particular case that textfile would only need a single entry of "F:" to make all programs launched from my game drive trigger the autoswitch)
- Make a TSR that overrides whatever I need to override in TOS to intercept program starts (I'm assuming it's going to be pexec)
The overridden program launch would behave somewhat like this:
- If the program that is being started is not in a folder or subfolder to an entry in that textfile then do nothing and let TOS do it's thing as usual, else:
- Set GPO so shifter is being outputted
- And then the tricky part...
Now we'll need to get rid of the bios overrides that the gfxcard driver has installed and replace them with normal shifter ones.
SetScreen, Getrez, Setpalette, Setcolor, Logbase, Physbase etc are the obvious ones but I'm sure there's going to be more. Probably some LineA stuff also.
- Now jump to the original TOS program launch so the game can start
- At program exit, restore GPO to what it was before. Also restore our bios overrides we installed in that tricky part above.
Or something like that.. we'll see when we get there I suppose
