You can install either up to 4 X 1MB SIMMs for 4MB total or, 4 X 4MB SIMMs or 2 X 8MB SIMMs for a total of 16MB. If you install 2 X 8MB SIMMs you may have some trouble as they mostly are double sided and they will not fit very well but I have got them to work in my 4000 and this does work! You have to install them into the 2nd and fourth socket (from right) to get this to work.
