The DDRMC5 supports two DRAM refresh options for LPDDR5/5X:
- All-bank refresh
- Per-bank Refresh
When all-bank refresh is used, all banks must be precharged before a refresh is issued. This means all banks are unavailable for the duration of the refresh operation (tRFC, e.g., 280 ns for 16 Gb). All-bank refresh makes the entire DRAM unavailable for about 7% of the time.
When per-bank refresh is used, each bank is issued a separate refresh command. This means while one bank is refreshed, the other banks are available. The duration of the per-bank refresh is shorter (tRFCpb, e.g., 140 ns for 16 Gb). Per-bank refresh makes each bank unavailable for about 3.5% of the time.
Using per-bank refresh can reduce and even eliminate the performance loss due to refresh. However, results heavily depend on traffic pattern and address mapping, and might in some cases be worse than all-bank refresh.