GS/OS should boot on a standalone Apple IIGS with 512K of RAM. If network
services are going to be used, 768K is required.
Check to see if you have a RAM disk created in the Control Panel. Perhaps
the RAM on the logic board or the memory expansion card is faulty; try
running diagnostics. The card could be misidentifying the amount of RAM
(because the jumpers aren't read correctly by the card even though they are
set correctly).