DDR5 DRAM components are available in three 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 16 Gb
components, 5600 speed grade.
| Feature | x4 | x8 | x16 | Performance Implication |
|---|---|---|---|---|
| Page size (x32) | 8 KB | 4 KB | 4 KB | |
| Banks | 32 | 32 | 16 | Fewer banks reduces the performance of random and multi-thread linear traffic patterns. |
| Bank Groups | 8 | 8 | 4 | 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 | 11.428 ns | 11.428 ns | 14.285 ns | Shorter tFAW improves performance of short random traffic pattern. |
| tRRD_L | 5 ns | 5 ns | 5 ns | None, all are the same. |
| tRRD_S | 8 nCK | 8 nCK | 8 nCK | None, all are the same. |