The LaserWriter 4/600 PS printer comes with 2MB of RAM pre-installed. An Apple-authorized service provider can install a 4MB memory expansion card (M4166G/A). The memory expansion card is designed specifically for the LaserWriter 4/600 PS. The printer is not equipped with industry-standard SIMM slots for installing additional memory.
The memory expansion card attaches to the I/O board on the printer, which requires the removal of the LaserWriter cover. Since removing the cover on a LaserWriter printer is not usually considered end-user replaceable part, Apple recommends you have the upgrade performed by an Apple-authorized service provider.