Examining the advances in mobile storage

At the University of New Hampshire InterOperability Laboratory (UNH-IOL), we are fortunate to be able to track technology developments in a number of areas, and watch as they go from sketches on a whiteboard to actual shipping products.

Sometimes these developments happen in their own bubbles, other times there are not so coincidental coincidences, where several industries are able to take advantage of technology originally developed for one community. We may be watching that happen right now as technologies originally developed for mobile are finding application in storage, and vice versa.

Mobile device makers tend to highlight high storage capacities of their devices. Lower end devices are typically in the 8-16 GB range, whereas higher end devices can have 128 GB or more. Most Android devices accept microSD cards, increasing their capacity further (currently microSD cards max out at 128 GB). But what are the technologies behind all this storage, and what's in store for them and the future of mobile storage?

Today's dominant mobile storage technologies
Today the dominant technologies for mobile storage are eMMC and microSD cards. Internal (i.e. non-user serviceable) storage is typically eMMC. Swappable and upgradeable microSD is what we know from use in cameras, phones, etc. The speed class on microSD refers to the read/write performance. The typical standard today is Class 10. Soon UHS (Ultra High Speed) cards will be available. Here are the key differences between eMMC and microSD:

eMMC:
Embedded, not upgradeable
400 MB/s

microSD Cards:
10 MB/s Class 10, up to 312 MB/s for future UHS cards
Easily swappable, upgradable

Most users don't think about the differences between these technologies. But when we look at the performance expectations on mobile devices, it's worth asking if these technologies can handle the coming performance demands for mobile devices.

What are these performance demands? Stepping through an example may be helpful. Consider a 4K mobile display operating at 60 frames per second (fps). How much bandwidth will it need?

Here's a simplified rough calculation:

4096x 2160 = 8847360 pixels
24 bits per pixel x 8847360 = 212336640 bits per frame
60 frames per second x 212336640 = 12,700,000,000 bits per second
12,700,000,000 bits per second = 1,590,0000,000B per second

That's 1.59 GB per second, nearly 4 times the throughput available from eMMC today.