Running disassembly on the system, VGA, and other add-in card BIOSes was often helpful. I recall figuring out how to cycle the palette faster than calling an interrupt, although it would still require vsync to prevent snow* and tearing.

* When updating the overscan region border color on some video cards DACs via direct port I/O, there would be random speckling of dots of previous and new colors like analog snow if synchronization to wait for the vertical blanking interval wasn't observed. This is the sort of shit emulation doesn't reproduce faithfully. It sometimes took having access to a lot of hardware to verify a program doing hardware-specific VGA tweaks worked correctly.