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Repair Windows errors before they cause bigger problemsFix Now →Scan for outdated or missing drivers - takes under a minuteDriver Scan →Yes—some DRAM-less NVMe SSDs can use a small, feature-specific portion of system memory through Host Memory Buffer (HMB). The SSD and host must both support HMB, and the memory is allocated for the drive controller—not used to store your ordinary files.
How an SSD can use system RAM
Host Memory Buffer is an optional NVMe feature introduced in NVMe 1.2. When a compatible host enables it, the host allocates a region of its DRAM for the SSD controller’s use. NVM Express describes this as memory set aside for the drive, with translation tables as one example of what it can hold. NVM Express
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This is most relevant to some DRAM-less NVMe SSDs, which do not have their own onboard DRAM. HMB does not turn system RAM into extra SSD capacity or a general-purpose cache for documents, photos, and applications. It is controller-managed working memory.
What the SSD uses HMB for
An SSD needs to translate the logical addresses used by the operating system into locations on its flash memory. In a peer-reviewed 2020 study, Kim and Kim found that the commercial DRAM-less drives they tested used HMB mainly to cache this flash-translation-layer address-mapping information—not as a general read cache or write buffer. That finding applies to the tested drives; manufacturers can implement the feature differently. Kim and Kim’s study
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How much RAM does an NVMe SSD use?
There is no universal HMB allocation. Its size is expressed in memory-page units in Microsoft’s NVMe documentation, and the configured amount depends on the drive’s implementation and host policy. Microsoft’s NVMe documentation
Kim and Kim reported different capabilities among the devices in their experiment: two could allocate between 8 MB and 480 MB in the study’s setup, while another could allocate 64 MB. These are experimental details for those tested devices, not a claim about what every SSD currently takes from Windows, Linux, or another host. Kim and Kim’s study
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Does HMB make a DRAM-less SSD as fast as one with onboard DRAM?
Not necessarily. Kim and Kim evaluated six SSDs: three DRAM-less models that supported HMB and three models with internal DRAM. In many of their results, the tested DRAM-less drives performed worse than the drives with onboard DRAM, while HMB improved performance for the HMB-capable drives. Those findings describe specific devices and workloads; they do not establish a universal performance ranking or guarantee. Kim and Kim’s study
For a purchase decision, check the exact model’s specifications rather than assuming all DRAM-less drives support HMB or behave alike. Relevant factors include:
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- Whether the SSD has onboard controller DRAM or is DRAM-less.
- Whether the manufacturer documents HMB support.
- Whether the host and interface support the feature.
- Capacity, warranty, and performance for the workloads you care about.
HMB is a technical design choice, not a reason on its own to reject or prefer a drive. The available study does not establish a best current retail model.
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