Atarian Computing wrote: Sun Jan 04, 2026 4:13 pm
Ok, I've been at it with AI. Let's see if it's any good.
Yeah I'm not a fan of spending time analysing and correcting AI "guesses".
To get any kind of sensible correctness out of it you would have to at least feed it the VME -> ISA adapter schematics for which the Mach64 TT driver was designed to work with. Best would also be the code for the GAL on that adapter but it's not open sourced.
However, from the schematics alone it's easy to see it pulls A23 low. With that I think it's safe to assume the driver wouldn't map it above the 8MB mark.
Also good idea would probably be to feed it the driver source, so it wont have to guess where it configures the linear framebuffer location based on what it picked up that some particular Windows or Linux driver that it found has done

It's completely up to the driver where it wants it so there's not much ground truth to be had there.
(The only thing that is set in stone is the default VGA compatible paged framebuffer that cards need to default to until a driver tells it otherwise.
Basically so that any PC since the dawn of time can use it for standard VGA stuff completely driverless)
M64VBE SWITCHES:
3 - Enable 320x200 & 320x240 modes in 8bpp, 15bpp, 16bpp and 24bpp.
Iirc this was an issue with the Mach32?
Yep the card fully supports those modes, and all standard VGA modes.
The Nova Mach32/64 drivers do not though.
These oddball MachXX cards are almost two separate graphics cards frankensteined into one.
One part is VGA compatible based on some old ATI something. This one is unaccelerated so no blitter in 320x200 etc.
The other is a clone of IBM8514A "CAD" card which has the acceleration stuff. This one can only do 640x480 and over.
The Nova MachXX drivers puts these cards in IBM8514A mode, which makes sense of course.
But it does not support switching between that and VGA.
It _can_ be possible by doing a man-in-the-middle attack on the Nova driver.
Detect if a program wants to go 320x200. Poke at the hardware directly to turn off the IBM8514, turn on VGA and set the resolution.
At this point the Nova driver can under no circumstances touch the card because it will still think it's running the IBM8514.
I did some experiments a while ago with that but as far as I remember I wasn't able to get it back to IBM8514 mode and hand it back to Nova reliably afterward.
And then I found the W32i and with that my motivation for messing with my Mach32 disappeared
