A Word on External SSDs: The Advent of UASP Even if you take the chip out and read it directly, you will be unable to access overprovisioned blocks, as chip-off extraction of eMMC chips still relies on sending commands to the eMMC controller. No interface is exposed to allow reading them from outside of the chip. Only the built-in controller has access to these data blocks. The area is invisible to physical acquisition, JTAG, ISP or chip-off since overprovisioned data blocks are not mapped onto available address space. There is no feasible way of extracting information from the overprovisioned area. Similar to SSD drives, eMMC chips may have an overprovisioned area that is non-addressable and inaccessible from the outside. Imaged eMMC chips have a much higher probability to retain data in trimmed blocks compared to SSD drives. In our experience, trimmed blocks that have not yet been erased may still be read by making a physical dump of the eMMC chip (via physical acquisition, JTAG, ISP or chip-off). Unlike SSDs, the eMMC standard does not define either DRAT (definite read after trim) or DZAT (definite zeroes after trim), which leaves it to the eMMC manufacturer to define what exactly the storage controller returns when an attempt is made to read a trimmed data block. So what happens to trimmed blocks located on an eMMC chip? Similar to an SSD drive, they may or may not be mapped out of the addressable space at any given time. Notably, eMMC standard correctly defines trimming of empty blocks. eMMC chips do not have the massive parallelism of SSD drives, and are much slower to read or write data. Even if an eMMC controller implements background garbage collection, it is going to work much slower compared to SSD drives since there is only a single channel available that is used for all read and write operations. many security features such as DRAT or DZAT). As a result, while eMMC may employ many of the same techniques as SSD drives (namely, overprovisioning, remapping, trimming and background erase), they may not implement some other options (e.g. Just like SSD drives, eMMC chips have a built-in controller, although eMMC controllers are considerably simpler and slower compared to those used in SSD drives. An eMMC chip is essentially an SD card that is built as a BGA chip soldered to the main board. Recent generations of Windows tablets, convertibles and ultra-light nettops (most of which are built around Intel Atom chip sets) employ a much smaller, cheaper and slower kind of storage in the form of eMMC chips. Traditionally, SSD drives have been large and expensive. eMMC storage has a lot in common with SD cards, and lacks sophistication and parallelism of SSD drives. ![]() You will find eMMC storage in most Android smartphones, Android and Windows tablets, and in some of the less expensive Windows convertibles, low-end netbooks and ultra-portable devices, particularly those equipped with smaller displays and Intel Atom CPUs. ![]() The Advent of eMMC StorageĮMMC is a storage specification for flash-based non-volatile storage used in many compact and mobile devices. In this part of the article, we will talk about external SSDs and eMMC and will cover trimming of eMMC. In the first part of this article, we reviewed different kinds of the most commonly used modern SSDs (M.2, PCI-E, NVMe devices) and talked about acquisition of these devices. What Has Changed in 2016 in the Way SSD Drives Self-Destruct Evidence.
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