I can't recall where, however I remember reading a super-interesting blog post of an old-time linux user complaining about his video card not being able to drive his displays.
He "solved" the issue by lowering the video card refresh rate (60hz -> 30hz) -- iirc.
Can't find that post anymore, but I always wondered if that approach would have allowed me to dive more displays with my integrated intel gpu. I was unable to go further than three 1920x1200 external displays (I had to sacrifice the fourth display, the laptop's built-in display)
You could do a lot with weird modelines in Xfree86.
I had not enough VRAM in a computer to do 16 bit 1024x768 but the difference was tiny. I think it needed a few tiny buffers for the mouse cursor and dragdropped icon, which was advanced 2d hardware acceleration at the time (Onion, belt, ...),and whatever memory was left just did not make it by a hair.
So I wrote a custom modeline to create an absolutely nonstandard videomode. I think the only requirement was that vert and horiz resolution were divisible by 4, so I did 1000 by 752 or something like that.
You had to make sure the dot clock was acceptable, or you could physically damage the CRT. Scary. So I did the calculations and tripple checked everything, then started a custom config with my thumb on the power button. It worked.
He "solved" the issue by lowering the video card refresh rate (60hz -> 30hz) -- iirc.
Can't find that post anymore, but I always wondered if that approach would have allowed me to dive more displays with my integrated intel gpu. I was unable to go further than three 1920x1200 external displays (I had to sacrifice the fourth display, the laptop's built-in display)