Visible to Intel only — GUID: qxe1576171034217
Ixiasoft
Visible to Intel only — GUID: qxe1576171034217
Ixiasoft
6.4.3.2. x4 DIMM Implementation
The necessary remapping is shown in the table below. You can implement this DQS remapping in either RTL logic or in your schematic wiring connections.
DIMM | Quartus® Prime EMIF IP | |||
---|---|---|---|---|
DQS0 | DQ[3:0] | DQS0 | DQ[3:0] | |
DQS9 | DQ[7:4] | DQS1 | DQ[7:4] | |
DQS1 | DQ[11:8] | DQS2 | DQ[11:8] | |
DQS10 | DQ[15:12] | DQS3 | DQ[15:12] | |
DQS2 | DQ[19:16] | DQS4 | DQ[19:16] | |
DQS11 | DQ[23:20] | DQS5 | DQ[23:20] | |
DQS3 | DQ[27:24] | DQS6 | DQ[27:24] | |
DQS12 | DQ[31:28] | DQS7 | DQ[31:28] | |
DQS4 | DQ[35:32] | DQS8 | DQ[35:32] | |
DQS13 | DQ[39:36] | DQS9 | DQ[39:36] | |
DQS5 | DQ[43:40] | DQS10 | DQ[43:40] | |
DQS14 | DQ[47:44] | DQS11 | DQ[47:44] | |
DQS6 | DQ[51:48] | DQS12 | DQ[51:48] | |
DQS15 | DQ[55:52] | DQS13 | DQ[55:52] | |
DQS7 | DQ[59:56] | DQS14 | DQ[59:56] | |
DQS16 | DQ[63:60] | DQS15 | DQ[63:60] | |
DQS8 | DQ[67:64] | DQS16 | DQ[67:64] | |
DQS17 | DQ[71:68] | DQS17 | DQ[71:68] |
Data Bus Connection Mapping Flow
- Connect all FPGA DQ pins accordingly to DIMM DQ pins. No remapping is required.
- DQS/DQSn remapping is required either on the board schematics or in the RTL code.
- An example mapping is shown below, with reference to the above table values:
FPGA (DQS0) to DIMM (DQS0) FPGA (DQS1) to DIMM (DQS9) FPGA (DQS2) to DIMM (DQS1) ... FPGA (DQS16) to DIMM (DQS8) FPGA (DQS17) to DIMM (DQS17)
When designing a board to support x4 DQS groups, Intel® recommends that you make it compatible for x8 mode, for the following reasons:
- Provides the flexibility of x4 and x8 DIMM support.
- Allows use of x8 DQS group connectivity rules.
- Allows use of x8 timing rules for matching. Intel® strongly recommends adhering to x4/x8 interoperability rules when designing a DIMM interface, even if the primary use case is to support x4 DIMMs only, because doing so facilitates debug and future migration capabilities. Regardless, the rules for length matching for two nibbles in a x4 interface must match those of the signals for a corresponding x8 interface, as the data terminations are turned on and off at the same time for both x4 DQS groups in an I/O lane. If the two x4 DQS groups were to have significantly different trace delays, it could adversely affect signal integrity.
About Pinout and Schematic Reviewing
When viewing x4 DQS mode in the Pin Planner, the 4 DQ pins do not have to be placed in the same colour-coded x4 group with the associated DQS/DQSn pins. This might look odd, but is not incorrect. The x4 DQS pins can be used as the strobe for any DQ pins placed within a x8 DQS group in an I/O lane.
Necessary checks to perform if the DQS groups are remapped in the RTL code
- In the Pin Planner, view x8 DQS groups and check the following:
- Check that DQ[7:0] is in x8 group, DQ[15:8] is in another DQS group, and so forth.
- Check that DSQ0 and DQS9 are in the DQS group with DQ[7:0], DQS1 and DQS10 are in the DQS group with DQ[15:8], and so forth. This is the DIMM numbering convention column shown in the table at the beginning of this topic.
- In the Pin Planner, view x4 DQS groups and check the following:
- Check that all the DQS signals are on pins marked S and Sbar.
- On the schematic, check the following DIMM connections:
- Check that DQSx on the DIMM maps to the DQSx on the FPGA pinout (for values of x from 0 to 17).
- Check that DQy on the DIMM maps to the DQy on the FPGA pinout. Note that there is scope for swapping pins within the x4/x8 DQS group to optimize the PCB layout.
Necessary checks to perform if the DQS groups are remapped on the schematic
- In the Pin Planner, view x8 DQS groups and check the following:
- Check that DQ[7:0] is in x8 group, DQ[15:8] is in another DQS group, and so forth.
- Check that DSQ0 and DQS1 are in the DQS group with DQ[7:0], DQS2 and DQS3 are in the DQS group with DQ[15:8], and so forth. This is the Quartus® Prime EMIF IP mapping shown in the table at the beginning of this topic.
- In the Pin Planner, view x4 DQS groups and check the following:
- Check that all the DQS signals are on pins marked S and Sbar.
- On the schematic, check the following DIMM connections:
- Referring to the table above, check that DQS has the remapping between the FPGA ( Quartus® Prime EMIF IP) and DIMM pinout (DIMM).
- Check that DQy on the DIMM maps to the DQy on the FPGA pinout. Note that there is scope for swapping pins within the x4/x8 DQS group to optimize the PCB layout.