the closest i ever encounter was when univbe provides 15bits colors modes for graphics cards
that discard that modes in favor for 16bits colors modes in the name of 'optimization'.

I remember encountering such dos games that complain the lack of 15bits color modes and refuse to run, fortunately univbe fix'd that.

4,096 colors however are not native to VGA/SVGA, they're used by other system such as Amiga

I realize HAM mode is proprietary, but it doesn't seem like there is anything special about a 12 bit color depth that would make it impossible for a PC to display, provided the driver supported it and there was enough RAM for the given resolution. But maybe there is some reason that wasn't done or we'd have seen it. I know that certain SGI machines supported a 12 bit color depth but I can't think of which ones right now. Personal Iris maybe? Any SGI folk lurking out there?

this problem may be similar to 24bit modes on pc that were once advertised with some products; iirc most cards would not even offer a real speedup from going 32->24 bits; others saved memory by packing data and slowed down a lot with this;

snorg wrote:

Does anyone know if 1 and 2MB cards can be forced into odd modes like a 12 bit color depth? I believe that a 2MB card is supposed to be capable of 15 bit color at 800x600, possibly 1024x768 butI was wondering if it is possible to force it to do an odd bit depth like 12 bit color to get higher colors in one of the resolutions that would not normally go above 256 colors (such as 1024x768 or 1280x1024). I have a Diamond Viper if that matters. I suspect that you would need to write custom drivers. If that's the case, that is out of my league, just wondered if maybe there was an undocumented mode.

Mathematically 2MB should suffice the memory needed for 1024*768*16bit which is equivalent to 1.5MB. There was an odd resolution designed around the 1K by 1K square, 1152*864, in order to exploit 1MB VRAM at 256 colors and 2MB VRAM at 16bit. Not sure if Viper supports that.

Looks like I will need to do some experimentation.

mrau wrote:

this problem may be similar to 24bit modes on pc that were once advertised with some products; iirc most cards would not even offer a real speedup from going 32->24 bits; others saved memory by packing data and slowed down a lot with this;

If 24bpp packed pixel mode is actually slower depends on the chipset. This is no generic fact.

elianda wrote:

If 24bpp packed pixel mode is actually slower depends on the chipset. This is no generic fact.

kinda right, but still i miss 16bit days; even today i switch to 16bit in the office on an intel gpu, just saves a lot of memory nad looks as good as needed;