Luckily, Apple derived a solution to this when it created 32-bit QuickDraw, and it is quite simple. Every time 32-bit QuickDraw access VRAM in the slot space, it uses a trap (SwapMMUMode) to temporarily switch the MMU into 32-bit mode, and when they are done, they use the same trap to switch back into 24-bit mode. There is also a trap (StripAddress) to strip out the flags from addresses that come from 24-bit mode so they are usable in 32-bit mode. This generally works, but on the original Mac II ROM, there was a bug that prevented more than 1 MB of slot space from being allocated per card. Apple released revised ROMs in November 1987 to fix this.