'Some games' need several megs of free, often contiguous RAM, like 900kB for each disk pre-loaded. So turning off preload in the slave for those games will help initially.Some game launchers can save precious memory too, e.g. XBench or TinyLauncher.
If the ACA does not offer software RAM upgrade via licensing then your option is to swap the card with a bigger one, probably a turbo.
edit: typo