When purchasing a solid-state drive (SSD), have you often come across terms like "SLC Cache," "HMB," or "DRAM-less design"? These technologies not only affect read and write speeds but also directly impact daily usability and product lifespan. As a professional storage solution provider, Juhor Precision Technology will guide you from the basics to fully understand the real functions of SLC Cache and HMB, helping you make smarter decisions when upgrading memory or replacing your SSD.
Before diving into SLC Cache and HMB, it's important to first understand the essence of "cache." Simply put, cache is a technology that trades space for time. Since hard drives are much slower in reading and writing than memory and CPU processing speeds, the system temporarily stores frequently accessed data in a high-speed area for quick retrieval. This significantly reduces waiting time and improves overall response efficiency. This mechanism is widely used in CPUs, memory, and even SSDs, serving as a key to smooth operation in modern computing devices.
Now let's focus on an important technology in SSDs—SLC Cache. It is not a separate physical cache chip but rather a high-speed area simulated by the controller on TLC or QLC flash memory operating in SLC mode. Because SLC stores only one bit of data per cell, it offers higher write speed and endurance, allowing this small "simulated zone" to significantly boost the SSD’s burst write performance.
So, how exactly is SLC Cache implemented? Depending on the controller design and manufacturer strategy, there are mainly three modes:
Fixed SLC Cache. This mode reserves a portion of flash memory exclusively for SLC simulation at the factory. The advantage is stable scheduling and consistent response; the downside is that it occupies OP (Over-Provisioning) space, reducing usable capacity.
Dynamic SLC Cache. Also known as Global SLC Cache. In this mode, the entire NAND space can dynamically serve as SLC cache based on current load. The more idle space available, the larger the usable SLC cache. This approach is more flexible, achieving a good balance between performance and capacity, though it demands higher requirements for controller algorithms and flash quality.
Hybrid SLC Cache.It's combining the strengths of the first two. It retains a small fixed SLC area as a baseline, while dynamically expanding additional cache space based on usage. This design balances stability and flexibility, commonly found in mid-to-high-end SSD products.
It should be noted that SLC Cache is mainly used for short-term high-speed write scenarios, such as copying files or launching programs. Once the cache is full, speeds drop back to native TLC/QLC levels. However, most daily operations fall within the cache range, so the actual user experience remains smooth.
Another frequently mentioned technology is HMB, short for Host Memory Buffer. Its emergence solves the core challenge of DRAM-less SSDs (solid-state drives without external DRAM).
Traditional SSDs rely on external DRAM chips to store the FTL (Flash Translation Layer) mapping table, which is critical for fast address lookup. However, adding DRAM increases cost, power consumption, and PCB design complexity. This is especially problematic for compact form factors like M.2 2280 and mSATA.
HMB technology was developed to address this issue. Based on the NVMe 1.2 and later protocol standards, the SSD controller can directly access a portion of the host system’s DRAM via the PCIe interface to store the FTL table. This eliminates the need for external DRAM while maintaining random read/write performance close to that of DRAM-equipped SSDs.
Specifically, HMB does not cache user data but focuses on managing flash address mapping. When the system needs to read a file, the controller uses HMB to quickly locate its physical position, greatly improving 4K random read/write efficiency. This technology is especially suitable for office work, web browsing, and light content creation, offering high cost-effectiveness with reduced power consumption and heat generation.
Currently, mainstream operating systems such as Windows 10/11 and Linux fully support HMB. As long as the host system has sufficient memory resources, HMB can deliver optimal performance.
Although both are referred to as "cache," SLC Cache and HMB address different aspects.
SLC Cache primarily optimizes write performance, especially for continuous writes and large file transfers;
HMB focuses on improving address lookup efficiency, enhancing random read/write and system responsiveness.
They can exist independently or work together in modern SSDs. For example, when copying large video files, SLC Cache accelerates the write process; while switching between background tasks and frequently accessing small files, HMB ensures the system remains smooth and lag-free. This complementary mechanism allows today’s DRAM-less SSDs to deliver excellent user experiences.
Faced with a wide range of products, how should consumers decide?
First, check whether the product specifications clearly state "SLC Cache Supported" or "HMB Enabled."
Second, make your choice based on usage scenarios:
For daily office work, students, or upgrading older systems: Recommend SATA or NVMe SSDs with HMB and dynamic SLC Cache—high cost-effectiveness and low power consumption.
For gamers and content creators: Suggest NVMe Gen3/Gen4 SSDs with dedicated DRAM and large SLC cache to ensure stable performance under prolonged heavy loads.
For industrial equipment and embedded systems: Consider mSATA or M.2 SSDs with HMB support, saving space while ensuring reliability.
Taking Juhor’s product line as an example, its NVMe M.2 SSDs generally adopt dynamic SLC Cache and HMB technology, suitable for mainstream desktops and laptop upgrades; while industrial-grade mSATA SSDs deliver excellent performance in low-power, wide-temperature environments thanks to HMB design.
SLC Cache and HMB are not marketing concepts but real technical solutions based on NVMe protocols and controller algorithms. They enable TLC/QLC SSDs to achieve a better balance among performance, cost, and power consumption. As a national high-tech enterprise, Juhor Precision Technology consistently integrates mature and reliable technologies into every DRAM memory and SSD product, providing users with truly practical storage upgrade solutions.
Whether upgrading DDR4/DDR5 memory or replacing SATA/NVMe SSDs, understanding these core technologies will help you make smarter choices.
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