Apple LaserWriter 12/640 PS - Manual (Page 124)

3 With the back cover properly positioned, replace the Phillips screws. Do not
overtighten the screws.
4 Next, configure the printer software to use the additional memory.
For configuration instructions, see “Configuring Your Printer Software for
New Options,” next.
If you want to check that you have properly installed the additional printer
memory, turn the printer back on and check the startup page. The amount of
printer memory should be listed there.
The printer does self-diagnostic tests each time it is turned on. During this
testing, the printer verifies the amount of memory installed. If the diagnostics
test determines that the installation is not correct, the Paper Out and the
Paper Jam lights will flash alternately. Check that you have installed the
SIMMs properly in the correct slots. If this does not resolve the problem,
contact an Apple-authorized dealer.
Configuring your printer software for new options
After installing more memory or paper options, the administrator or the user
needs to update the printer software on each computer connected to the
network. You can reconfigure the printer software using the Chooser on
Mac OS–based computers or the Windows Setup dialog box on
Windows-based computers.
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