It may also cause performance issues with the rest of the system if it is not designed with the fact in mind that some RAM will be 'taken away' by graphics.
The memory in these machines is simply one fast pool (2.1 GB per second in 1996) shared between system and graphics.
Sharing is performed on demand, including pointer redirection communication between main system and graphics subsystem.
Graphics display was facilitated by the use of an expansion card with its own memory plugged into an ISA slot.
The exact size of the video memory could be reconfigured by software to meet the needs of the current program.