HP ProLiant DL580 G3 Server - Manual (Page 59)

Hardware options installation 59
3.
Lower the processor module lever, and pull the module out of the server.
4.
Release the latch, and open the cover to expose the processors.
Installing a processor
Processors must be installed in the following order: processor 1, processor 2,
processor 4, and processor 3.
Server PPMs provide the proper power to each processor. Each PPM must be
installed in the slot adjacent to its processor.