DRAM cache
A small DDR memory chip on an SSD that stores the flash translation layer (FTL) map. Drives with DRAM have predictable random-access performance; DRAM-less drives degrade under heavy use.
An SSD's flash translation layer maps logical block addresses to physical NAND locations. With every write the map updates. Storing this map in fast DRAM keeps random I/O predictable.
DRAM-less drives
Budget SSDs omit DRAM and instead use Host Memory Buffer (HMB) — a slice of system RAM allocated by the NVMe driver. Performance is fine for light use but degrades as the drive fills past 70%, especially on random 4K workloads.
How to spot a DRAM-less drive
- Marketing rarely mentions it.
- Tear-down photos and review databases (techpowerup, tomshardware) list the controller and cache config.
- Price: drives well under $50/TB are usually DRAM-less.
In comparisons
For a OS / game drive, DRAM-less is fine. For a daily-driver SSD that will fill to 80%+, DRAM-equipped drives stay snappy years into use. The TLC + DRAM combination is the modern enthusiast baseline.