HP Color LaserJet 8550 Multifunction Printer series - Manual (Page 209)

208 A DIMM Installation EN
To install a DIMM
1 Synchronous DRAM (memory)
DIMMs must be installed in pairs.
2 Print a configuration page. Next turn
the printer off and disconnect it from
its power source. Locate the
formatter board on the left rear of the
printer.
3 Loosen the two thumb screws by
hand or with a #2 Phillips screwdriver.
4 Slide the formatter board out and lay
it on a flat, grounded surface.