DDR4 Component Choice - 1.0 English

Versal Adaptive SoC Programmable Network on Chip and Integrated Memory Controller 1.0 LogiCORE IP Product Guide (PG313)

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1.0 English

DDR4 DRAM components are available in 3 variants: x4, x8, and x16. The choice of component is often determined by factors such as cost, power, board space, etc. Here, only the performance impact is considered. The following table compares various features of the DRAM components and their performance impact.

Note: Data shown is for 8 Gb components, 3200 speed grade.
Table 1. DDR4 Component Choice Trade-Offs
Feature x4 x8 x16 Performance Implication
Page size (x64) 8 KB 8 KB 8 KB None, all are the same.
Banks 16 16 8 Fewer banks reduces the performance of random and multi-thread linear traffic patterns.
Bank Groups 4 4 2 Fewer bank groups reduces the MC's ability to reorder and achieve "short" timing.
Data Mask No Yes Yes Without data mask, any partial write requires a read-modify-write operation, reducing overall performance.
tFAW 13 ns 21 ns 30 ns Shorter tFAW improves performance of short random traffic pattern.
tRRD_L 4.9 ns 4.9 ns 6.4 ns Shorter parameter improves overall performance.
tRRD_S 3.3 ns 3.3 ns 5.3 ns Shorter parameter improves overall performance.