I implemented the proper color palette behavior. It's the restriction to the 16 CGA colors in 200 lines EGA modes, and the layout of these colors is not obvious. Now I'm confident I'm doing the same thing as good VGA BIOS implementations.

I also added the other EGA color graphics modes. Mode 0Eh (640x200 16 colors) is often utilized by later VGA games as the EGA fallback (notably some Lucas Arts games), with heavy dithering. And mode 10h (640x350 16 colors).

Text modes other than mode 3 are also ignored on Turing+, so 40 column text modes are also broken. For now I added mode 1 (40x25 color text mode), it works with a 3D Tetris game named Block Out, which uses hi res EGA graphics in game but 40x25 text mode menus. So now this game is also fully working with an RTX. 40 column text mode doesn't behave very well in the command line though, I still haven't figured out why.

I don't handle monochrome modes, nor CGA modes. For these, I might make another TSR (CGAFIX?) as to not increase the TSR size for those that don't need them.

Thank you. Everything works great.
I can play Dangerous Dave again on my RTX 3060 Ti.

Oooh I gotta try this.. I don't mind if the TSR covers all CGA/EGA even if it goes a little larger.. I have space in upper memory to toss it in.. better than having to load two TSRs.

Shame that this stuff should actually exist in the card's BIOS.. but RTX cards have a lot of BIOS issues beyond just ignoring those legacy modes..

I'm wondering also if there is something that can be done to somehow drive the monitor to 4:3 aspect ratio?

Gave it a try. Prince of Persia EGA looks great. Keen 4 looks great and scrolls great too, except anywhere there is text. Text comes garbled whether in the main menu or in messages during the game. Not sure why is that...

I've found some limitations of faking graphics modes behind the back of the graphics card. Some other vBIOS functions depends implicitly on the current mode, like switching video page (as there is an address calculation that depends on the resolution, bit depth, ...), as done by Cosmo's Cosmic Adventure, so every two frames we get garbled graphics. It can also explain the problems in 40 columns command line, the vBIOS still thinks it has 80 columns of real estate. It will be a significant amount of work to do all the book-keeping and reimplementing all these functions, provided that's possible. I removed all the broken features for now (so you still can't go past Cosmo's Cosmic Adventure EGA detection) not to bloat the TSR with useless code.

Other than that, I added monochrome text modes and a preliminary CGA modes support. Color palette selection is yet another mechanism, via vBIOS functions that are unsurprisingly non functional, so I'll have to reimplement them too, which shouldn't be too hard this time. So for now you will only have the default bright black, cyan, magenta, white palette. And text isn't working at all in CGA graphics modes, I haven't figured out why yet. That's already enough for some CGA games like Prince of Persia. In Alley Cat, when in the menu, the screen is all black, you have to blindly type 'N' (for no joystick), then 'K' (for Kitten difficulty, this game is already so hard...), then any key, and you can play. Unpon exiting (Ctrl+Y), as the game doesn't revert to text mode, you have to blindly enter 'mode 80' or 'cls' to bring back the prompt on screen.

Speaking of reducing the number of TSRs, I integrated the fix of Falcosoft's MSKVBEF7 into it, because I don't see a situation where you wouldn't want it on a modern system.

wbahnassi wrote on Today, 13:25:

I'm wondering also if there is something that can be done to somehow drive the monitor to 4:3 aspect ratio?

I can't have my monitor to display anything with the 4:3 aspect ratio when connected via DisplayPort. With HDMI I have the option to respect the 4:3 aspect ratio for 4:3 or 5:4 resolutions, but modern graphics card seem to scale everything to the screen preferred resolution. It's possible to modify the EDID of the screen to prefer a 4:3 resolution instead, but a safer option that I haven't tested may be this one.

wbahnassi wrote on Today, 17:10:

Gave it a try. Prince of Persia EGA looks great. Keen 4 looks great and scrolls great too, except anywhere there is text. Text comes garbled whether in the main menu or in messages during the game. Not sure why is that...

This I think comes from the fact that it's not possible to read the VGA latches registers directly, since at least the Geforce 6 series. On one hand it's an undocumented VGA feature, but on the other hand it was so ubiquitous that a lot of software relied on it, Commander Keen 4-6, even Windows 9x default VGA driver (there are a lot of artifacts there). So yeah it's a shame, but quite ancient bug, and sadly we can't fix it with real mode code.