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One free scan finds every outdated or missing driver and matches the right update for your exact hardware.Free scan · exact hardware matchSome DRAM-less NVMe SSDs can use a small, reserved portion of your PC’s memory through Host Memory Buffer (HMB). It is not a large general-purpose cache for files, and it does not add physical DRAM to the SSD. HMB can help with some access patterns, but it does not guarantee the performance of a drive with onboard DRAM. The evidence here comes from a 2020 academic study and named product reviews—not a first-person test—so results are tied to those specific drives and workloads.
What Host Memory Buffer does
Host Memory Buffer is an NVMe feature introduced with NVMe 1.2. When both the SSD and operating system support it, the drive can request a portion of host DRAM for an internal purpose chosen by its manufacturer. The drive does not gain onboard DRAM, and HMB does not turn all of your PC’s memory into a broad read-and-write cache. A peer-reviewed study describes the feature and its dependency on support from both the drive and the operating system.
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In the six drives examined in that 2020 study, the tested HMB models primarily used host memory to cache address-mapping information: data that helps the SSD locate content in its NAND flash. That is evidence about those particular drives, not a guarantee that every manufacturer implements HMB identically; SSD internals are often proprietary.
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No general rule says it does. In the study, researchers compared three commercial DRAM-less HMB drives with three drives that had internal DRAM, using light and heavy sequential and random read-and-write workloads. DRAM-less drives performed worse in many test results, while HMB improved performance in some patterns, including random reads. The findings show why the drive design and workload matter; they do not establish one universal percentage benefit for HMB.
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HMB can therefore help a DRAM-less drive handle some internal bookkeeping without making it equivalent to every onboard-DRAM model. A short benchmark or a single read test cannot answer how the drive will behave under a different workload.
Why everyday speed and long writes can tell different stories
Sequential speed specifications and short tests do not necessarily describe sustained writing after a drive’s secondary write cache is exhausted. A PCWorld review published April 22, 2025 reported strong everyday performance from the tested 2 TB Teamgroup MP44Q, an HMB PCIe 4.0 QLC SSD. In that review’s transfer conditions, writes slowed to 100–135 MB/s after the secondary-cache condition was exceeded.
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That figure is specific to the reviewed 2 TB sample and its workload, not an HMB-wide limit. PCWorld also cautioned that performance can vary with capacity and drive components. The result illustrates why sustained-write behavior deserves its own check, especially if your work involves moving large files or writing substantial amounts of data at once.
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What manufacturer specifications can—and cannot—tell you
Samsung’s 2021 announcement described the Samsung 980 as a DRAM-less consumer SSD using HMB, with maximum sequential specifications of 3,500 MB/s read and 3,000 MB/s write. Those are Samsung’s published maximum specifications, not independent measurements. Samsung’s announcement identifies the drive’s HMB design, while Samsung’s Canadian product page says performance varies with firmware, system, and hardware configuration.
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A sequential maximum is useful for understanding a product’s advertised capability, but it does not establish random-read performance, cache-exhausted write speed, or how another capacity or revision will behave. Keep vendor figures distinct from independent measurements.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.How to compare HMB and onboard-DRAM SSDs
For a meaningful comparison, line up the exact models and capacities and look for results that reflect the work you will do. Check that a quoted figure is identified as a manufacturer specification or an independent measurement.
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- Exact capacity and revision: Different capacities or component revisions may perform differently; do not assume a review of one version describes every version.
- Workload and method: Note whether testing used sequential or random operations, reads or writes, and light or heavy workloads.
- Random-read behavior: HMB improved some random-read patterns in the 2020 study, but the study did not establish a universal advantage.
- Long sustained writes: Look for results after the secondary write cache is exceeded if large transfers matter to you.
- NAND type: Include it in the comparison, but do not treat it alone as a substitute for workload-specific measurements.
- Drive condition: When results are available, note the drive’s fill state and other test conditions; they can affect whether a comparison reflects your use.
If you mostly need responsive everyday storage, an HMB drive may be a reasonable fit; the cited review found strong everyday performance for its tested MP44Q sample. If you frequently write large amounts of data, prioritize sustained-write results for the exact capacity you are considering rather than relying on a short benchmark or advertised sequential maximum.
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