External Memory Interfaces Intel Agilex® 7 M-Series FPGA IP User Guide

ID 772538
Date 10/02/2023

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Document Table of Contents x4 DIMM Implementation

DIMMS using a x4 DQS configuration require remapping of the DQS signals to achieve compatibility between the EMIF IP and the JEDEC standard DIMM socket connections.

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.

Table 114.  Mapping of DQS Signals Between DIMM and the EMIF IP
DIMM   Intel® Quartus® Prime EMIF IP
DQS0_A DQ[3:0]_A   DQS0 DQ[3:0]_A
DQS5_A DQ[7:4]_A   DQS1 DQ[7:4]_A
DQS1_A DQ[11:8]_A   DQS2 DQ[11:8]_A
DQS6_A DQ[15:12]_A   DQS3 DQ[15:12]_A
DQS2_A DQ[19:16]_A   DQS4 DQ[19:16]_A
DQS7_A DQ[23:20]_A   DQS5 DQ[23:20]_A
DQS3_A DQ[27:24]_A   DQS6 DQ[27:24]_A
DQS8_A DQ[31:28]_A   DQS7 DQ[31:28]_A
DQS4_A CB[3:0]_A   DQS8 CB[3:0]_A
DQS9_A CB[7:4]_A   DQS9 CB[7:4]_A
DQS0_B DQ[3:0]_B   DQS10 DQ[3:0]_B
DQS5_B DQ[7:4]_B   DQS11 DQ[7:4]_B
DQS1_B DQ[11:8]_B   DQS12 DQ[11:8]_B
DQS6_B DQ[15:12]_B   DQS13 DQ[15:12]_B
DQS2_B DQ[19:16]_B   DQS14 DQ[19:16]_B
DQS7_B DQ[23:20]_B   DQS15 DQ[23:20]_B
DQS3_B DQ[27:24]_B   DQS16 DQ[27:24]_B
DQS8_B DQ[31:28]_B   DQS17 DQ[31:28]_B
DQS4_B CB[3:0]_B   DQS18 CB[3:0]_B
DQS9_B CB[7:4]_B   DQS19 CB[7:4]_B

Data Bus Connection Mapping Flow

  1. Connect all FPGA DQ pins accordingly to DIMM DQ pins. No remapping is required.
  2. DQS/DQSn remapping is required either on the board schematics or in the RTL code.

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. Adhere 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. Trace delays for two nibbles packed within the IO12 lanes are matched using the same guidelines as a single x8 byte lane.