What is the rule of the SPD address assignment if there are more that 8 dimm slots?
The board tht I am working on has 2 process. Each of them has 6 DIMM slots. If you plug 1 dimm into each slot, the SPD address will be, Channel PCB ---------------- P0: DIMMA0 50h DIMMA1 51h DIMMA2 52h DIMMB0 53h DIMMB1 54h DIMMB2 55h P1: DIMMA0 50h DIMMA1 51h DIMMA2 52h DIMMB0 53h DIMMB1 54h DIMMB2 55h If you plug 1 dimm in P0DIMMA0 and the other in P1DIMA0, the SPD address will be 50h and 55h. So I am confused. If we got an active spd 0x50 on the SMBUS, what will it be? It seems that we can not plug more that 8 dimm even if we have 12 slots, correct? Zheng
2010/7/31 Zheng Bao <fishbaoz@hotmail.com>:
The board tht I am working on has 2 process. Each of them has 6 DIMM slots. If you plug 1 dimm into each slot, the SPD address will be, Channel PCB ---------------- P0: DIMMA0 50h DIMMA1 51h DIMMA2 52h DIMMB0 53h DIMMB1 54h DIMMB2 55h P1: DIMMA0 50h DIMMA1 51h DIMMA2 52h DIMMB0 53h DIMMB1 54h DIMMB2 55h If you plug 1 dimm in P0DIMMA0 and the other in P1DIMA0, the SPD address will be 50h and 55h. So I am confused. If we got an active spd 0x50 on the SMBUS, what will it be?
Are you sure the wiring is correct? Can you plug the DIMM into P1DIMMB2 and see what SPD address it has? This could be a simple case of an error in the wiring. What does the standard say about SPD addressing of DIMMs? It's more than a 3 bit address and it seems we must have more addresses in the definition. ron
On 7/31/10 4:56 PM, Zheng Bao wrote:
The board tht I am working on has 2 process. Each of them has 6 DIMM slots. If you plug 1 dimm into each slot, the SPD address will be, Channel PCB ---------------- P0: DIMMA0 50h DIMMA1 51h DIMMA2 52h DIMMB0 53h DIMMB1 54h DIMMB2 55h P1: DIMMA0 50h DIMMA1 51h DIMMA2 52h DIMMB0 53h DIMMB1 54h DIMMB2 55h If you plug 1 dimm in P0DIMMA0 and the other in P1DIMA0, the SPD address will be 50h and 55h. So I am confused. If we got an active spd 0x50 on the SMBUS, what will it be? It seems that we can not plug more that 8 dimm even if we have 12 slots, correct?
Zheng
There is probably an smbus hub for switching between the P0 and P1 SPD ROMs. Check out src/mainboard/tyan/s4880/romstage.c for an example of a board with smbus hub. Stefan
2010/7/31 Stefan Reinauer <stefan.reinauer@coresystems.de>:
On 7/31/10 4:56 PM, Zheng Bao wrote:
The board tht I am working on has 2 process. Each of them has 6 DIMM slots. If you plug 1 dimm into each slot, the SPD address will be, Channel PCB ---------------- P0: DIMMA0 50h DIMMA1 51h DIMMA2 52h DIMMB0 53h DIMMB1 54h DIMMB2 55h P1: DIMMA0 50h DIMMA1 51h DIMMA2 52h DIMMB0 53h DIMMB1 54h DIMMB2 55h If you plug 1 dimm in P0DIMMA0 and the other in P1DIMA0, the SPD address will be 50h and 55h. So I am confused. If we got an active spd 0x50 on the SMBUS, what will it be? It seems that we can not plug more that 8 dimm even if we have 12 slots, correct?
Zheng
There is probably an smbus hub for switching between the P0 and P1 SPD ROMs.
Check out src/mainboard/tyan/s4880/romstage.c for an example of a board with smbus hub.
Another example is in the serengeti_cheetah romstage.c activate_spd_rom(). Marc -- http://se-eng.com
participants (4)
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Marc Jones -
ron minnich -
Stefan Reinauer -
Zheng Bao