image of ADATA SD700 USB-A SSD


SSD Specification and Info

ADATA SD700 is an Entry-Level SATA SSD produced and sold by ADATA. The device comes with USB 3.2 Gen 1x1 interface and USB-A form factor - a good fit for both desktop and laptop computers. This SSD has a maximum sequential read-write speed of up to 440/430 MB per second, making it ideal for gaming and workstation PCs.

ADATA SD700 is equiped with DRAM memory, and a TLC NAND flash memory with 32/64 cell layers.


InterfaceUSB 3.2 Gen 1x1
Form factorUSB-A
ControllerSMI SM2258
ConfigurationSingle-core, 4-ch, 8-CE/ch
NAND brandMicron
R/W speed440/430 MB/s
TierEntry-Level SATA
ManualADATA SD700

NAND type

ADATA SD700 is using a TLC (3 bits per cell) NAND manufacurted by Micron with 32/64 cell layers on top of each other.

The TLC is the most common type of SSD NAND flash memory found on the market at the moment. It is faster, less durable, but still cheaper than the other, more expensive variants - SLC and MLC.

The main advantage of this type of NAND chips is the fact that the cost per gigabyte is much lower, allowing high capacity SSDs at affordable price.

The Controller

ADATA SD700 is using SMI SM2258 SSD controller to connect the NAND memory to the USB 3.2 Gen 1x1 interface. The controller has Single-core, 4-ch, 8-CE/ch configuration.

Typically, SSD controllers are microprocessors. In this case we have Single-core, 4-ch, 8-CE/ch processor responsible for controlling the SSD in such way, so that the data coming from the interface can be stored on to the NAND flash memory.

Some SSDs have simpler controllers with fewer communication channels and less cores.

Among other things, the controller also manages the SLC caching, optimizing the DRAM cache, encryption, LDPC, garbage collection, wear-leveling as well as TRIM

DRAM Cache

ADATA SD700 has a separate DRAM chip to store the SD mapping tables. DRAM cache speeds up the data access significantly compared to the DRAM-less models.

As soon as the OS requests some data from the SSD, the SSD needs to know exactly where it is on the drive. Because garbage collection moves the data constantly, the controller relies on the mapping tables to locate it.

These tables are stored in DRAM cache, where they are accessed much more quickly than in NAND flash.

Therefore, SSDs with DRAM-less architecture have more random write and read operations. This makes the device perform worse and last shorter if they are not HMB enabled.

HMB Support

There is no HMB architecture available on the ADATA SD700 to store the mapping tables. The device either doesn't support the architecture or uses DRAM cache.

The HBM is used to reduce the cost of production of NVMe SSDs with DRAM Cache, SSDs with this type of controllers can leverages the host system's DRAM instead of an onboard DRAM chip to host the FTL mapping table used by flash storage.