HP Color LaserJet 8550 Multifunction Printer series - Manual (Page 208)

EN Supported DIMMs 207
A
DIMM Installation
Supported DIMMs
The printer supports the following types of DIMMs (dual inline
memory modules):
z ROM
z Synchronous DRAM
EDO (extended data out) or Fast Page Mode DIMMs are not
supported.
Installing DIMMs
The printer supports ROM (font) and synchronous DRAM
(memory) DIMMs. ROM (font) DIMMs need not be installed in a
specific configuration. DRAM (memory) DIMMs must be installed
in synchronized pairs: two DIMMs with the same amount of
DRAM (memory) are installed in slots such as 1 and 2 (see
task
5 on page 209 ). A ROM (font) DIMM can be installed in
slots 1 and 3, and slot 2 should be empty. However, ROM (font)
DIMMs cannot be installed as pairs (in corresponding left and
right slots).