ANSWER: 9 DIMM slots per processor.
When there are two processors, AR360 F1 can support 18 DIMM.
When there is only one processor, AR360 F1 can support 9 DIMM. (In this case, DIMM installed at DIMM slots
1A/1B/1C, 2A/2B/2C and 3A/3B/3C of processor 2 cannot be detected).