6402 datasheet(24/250 Pages) INTEL

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FBD Channel Interface

Intel® 6400/6402 Advanced Memory Buffer Datasheet

DRAM SCLK is placed at the center of the command window which adds an additional

6UI of delay. The DRAMs are programmed with a TRead_Latency of 4. The DQS strobes

are centered when they get to the AMB (3UI delay) and the data takes an additional 10

UI to propagate from the DDR I/O to the NB FBD I/O (including setup time at NB FBD

and CRC generation) before it can be clocked into the NB FBD for transmission. The

total delay without including the DRAM access time in this case is (10 + 6 + 3 + 10UI)

29UI. The CMD2DATANXT.DLYFRMS will be programmed with a value 2 and the

CMD2DATANXT.DLYFRAC with 5UI. If the AMB supports only a 2UI granularity, then the

values should be 2 frames and 6UI respectively. If an AMB does not support sub-frame

delays, it is expected that the value in SPD will be round up the to the nearest frame.

Any additional delays caused by rounding up should be supported by additional

buffering in the DDR I/O.

The above figure shows the last arriving data from the DDR. It is expected that any

data arriving earlier than this, due to differences in routing, and so forth, is buffered up

in some way inside the DDR I/O. The expectation is that all AMBs (last and

intermediate) unload the data from the DDR I/O with the timing specified by the

TCMD_To_DATA. The Last AMB is expected to be able send data on the NB links with no

additional delay added, if C2DINCRCUR.INCRDLY is 0. Any additional delay needed due

to the value programmed in C2DINCRCUR.INCRDLY register in the last AMB or to delay

the data in intermediate AMB before the merge, is handled by FIFOs in the AMB core.

In the above figure, it is assumed that the AMB can place the clocks in position shown

above. If this is not the case, then additional delays due to non-optimal placement of

the clocks should be taken into account to calculate the total delay to be programmed

into the SPD.

6402 Datasheet(PDF) 24 Page - Intel Corporation