Flash Memory Matters: NAND Solutions for Every Need

FMM Decisions e-MMC or UFS

Decisions, Decisions….e-MMC or UFS?

Memory products that incorporate NAND die and a hardware controller in one package are referred to as managed flash. KIOXIA offers two different technologies for managed flash: e-MMC (embedded MultiMediaCard) and UFS (Universal Flash Storage).

e-MMC, derived from a removable MMC chip, was the first1 standardized managed flash solution. It was developed roughly 17 years ago, with the idea of creating a device with an embedded controller that would manage bad blocks, error correction, wear levelling and garbage collection. Managing the flash within the memory device provides a reduction in workload for the host-side processor and an improvement to overall efficiency and time-to-market.

e-MMC gained adoption in the market and was initially used in many different applications, from PDAs to tablets and smartphones. The end uses for e-MMC continue to grow in the market and it continues to be a very successful memory technology.

So, with the wide adoption of e-MMC, the question became: “Why do we need another managed flash product?” The problem was that e-MMC device capabilities had reached a bottleneck; and there was no chance for it to get bigger, better or faster. Interface speeds couldn’t be enhanced, and new features and functions couldn’t be added. As applications, particularly mobile devices, continued to evolve and become more like minicomputers, it was apparent that another technology was needed. 

Enter UFS in 2014. When looking at how UFS differs from e-MMC, the two most important attributes to keep in mind are speed and capacity.

When we consider interface speed, UFS far exceeds that of e-MMC. UFS has a full duplex/serial interface, meaning that data can be sent and received simultaneously. e-MMC, on the other hand, has a half-duplex/parallel interface. This restriction allows only one data line to send or receive data at any time. In terms of speed, e-MMC can reach a maximum interface speed of 400 megabytes per second (MB/sec)2, whereas UFS v4.0 devices achieve speeds of up to 4640Mb/sec (more than 10x that of e-MMC) - with the possibility of even faster speeds in the future.

In addition to interface speed, UFS far exceeds the capabilities of e-MMC in random and sequential reads and writes. To put this into perspective, the newest UFS version delivers sequential writes of 3800MB/sec vs. e-MMC v5.1 at 150MB/sec. UFS outperforms e-MMC– making it the technology of choice for today’s application-heavy mobile products that need to provide quick access for optimal user experiences.

You might be asking yourself, “If UFS is so much faster, why is e-MMC still around?” Good question. As mobile applications migrated to UFS, a variety of new end products saw e-MMC as a cost savings over traditional SLC NAND and recognized the benefits of a managed solution.  Also, there are many applications today that don’t need the performance and capacity benefits that UFS brings, and these applications will continue to use e-MMC as long as it is available in the market. Applications in this category include consumer products with mid-range storage requirements, such as tablets, personal computers, point of sale devices, and other portable handheld devices, as well as Smart TVs and Smart NICs (Network Interface Cards).

In addition, e-MMC is a very common interface and is supported by most SoCs today, while UFS is still mainly supported by mobile and automotive SoCs (although this continues to expand).

It’s for all of these reasons that KIOXIA continues to offer e-MMC products with capacities from 4GB to 128GB. Our UFS offerings range in capacity from 32GB to 1TB.

When it comes to managed flash, what truly matters is aligning performance and capacity needs with the appropriate technology, whether it's the robust capabilities of UFS or the more modest requirements met by e-MMC. In either case - rest assured, KIOXIA offers tailored solutions to fit your specific needs.


1: Developed in 2006 by JEDEC and the MultiMediaCard Association.

2: e-MMC’s maximum clock speed is 200MHz in 8-bit DDR mode. Beyond this, signal integrity diminishes.

Universal Flash Storage (UFS) is a product category for a class of embedded memory products built to the JEDEC UFS standard specification. Due to its serial interface, UFS supports full duplexing, which enables both concurrent reading and writing between the host processor and UFS device.

Read and write speed may vary depending on various factors such as host devices, software (drivers, OS etc.), and read/write conditions.

All other company names, product names and service names may be trademarks of their respective companies.

Definition of capacity: KIOXIA Corporation defines a megabyte (MB) as 1,000,000 bytes, a gigabyte (GB) as 1,000,000,000 bytes and a terabyte (TB) as 1,000,000,000,000 bytes. A computer operating system, however, reports storage capacity using powers of 2 for the definition of 1GB = 2^30 bytes = 1,073,741,824 bytes and 1TB = 2^40 bytes = 1,099,511,627,776 bytes and therefore shows less storage capacity. Available storage capacity (including examples of various media files) will vary based on file size, formatting, settings, software and operating system, and/or pre-installed software applications, or media content. Actual formatted capacity may vary.

The views and opinions expressed in this blog are those of the author(s) and do not necessarily reflect those of KIOXIA America, Inc.

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