Two SSDs can advertise the same capacity and the same sequential read speed, yet sell at very different prices. Often the explanation is one small chip: DRAM. Here is a practical breakdown of what it does and when it matters.
What DRAM does inside an SSD
Every SSD keeps a mapping table (the Flash Translation Layer, or L2P table) that records where each piece of data physically lives on the NAND chips. The controller consults this table on every single read and write. DRAM is roughly 100x faster than NAND, so keeping the table in DRAM cuts latency dramatically. The industry rule of thumb is about 1 GB of DRAM per 1 TB of capacity.
What "DRAMless" means (and what HMB is)
A DRAMless SSD simply skips that chip to cut costs. It then stores the mapping table in the slower NAND itself, or borrows a small slice of your system RAM through a feature called HMB (Host Memory Buffer), part of the NVMe 1.2 spec. HMB typically borrows only 16–64 MB, so your RAM barely notices, but it needs a supporting controller, firmware, and OS driver to work. Classic budget DRAMless drives include the Kingston A400 and older WD Green models.
Where the difference actually shows up
- Sequential transfers (copying a 10 GB video): nearly identical.
- Random small-file access (booting Windows, opening dozens of apps, VMs, databases): DRAM wins clearly, because the mapping table is consulted thousands of times per second.
- Very long sustained writes: many DRAMless drives rely on an SLC cache; once it fills during a huge copy, speeds can drop until the transfer finishes.
- Endurance and power: DRAMless puts extra wear on NAND (sometimes reflected in shorter warranties), but it also draws less power and fits on single-sided PCBs for thin laptops.
I tested the underlying principle myself
I don't have two physical SSDs to race, so I tested the principle in my Linux lab: writing 256 MB with RAM page cache hit 675 MB/s, versus 184 MB/s with direct I/O bypassing the cache. More dramatically, 4,000 random 4 KB writes ran at 164 MB/s with cache and collapsed to 697 kB/s without it, roughly 235x slower. That is an analogy, not a real SSD benchmark (the real-world gap is far smaller, especially with HMB), but the principle is identical: fast memory matters most for small random operations like mapping-table lookups.
Which should you buy?
- OS / system drive: get one with DRAM.
- Second drive for games and archives: DRAMless with HMB is plenty, and the savings can buy you more capacity.
- Thin, battery-sensitive laptop: DRAMless is efficient and compact.
- Budget upgrade from an HDD: even the cheapest DRAMless SSD is enormously faster than any spinning drive. Don't delay the upgrade.
Full Indonesian version with comparison table, FAQ, and lab screenshots: https://www.miftahulrizki.eu.org/2026/10/ssd-dram-vs-dramless-apa-bedanya-dan.html
Related reading: do SSDs need defragmenting?
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