What is Adata’s “pseudo-SLC” mode flash?

Computex 2014: High speeds from smart firmware coding

Adata logoAdata revealed a brilliant little bit of technology to SemiAccurate at Computex, “psuedo-SLC” mode for MLC flash. This little trick is easy to explain and also succinctly lays out how they managed to get to UHS-1 SC3 speeds.

You might recall the Adata XPG SD cards from a few weeks ago which claim 95MBps read and 85MBps writes out of a humble SD form factor. This is seriously fast, faster than anything on the market can probably use at the moment. How did Adata get those speeds out of pedestrian MLC flash? SLC would be both shatteringly expensive and very limited in capacities so that is obviously out. XPG cards cap out at 64GB and while not cheap are hardly SLC device expensive.

The idea is pretty simple to explain, treat MLC flash like SLC, instead of two bits per cell, treat it as one bit. This speeds up reads and writes but also halves capacity, one step forward one step back. Given the speeds they could coax out of the devices, we consider this a serious win even with the lowered storage space.

In the end Adata just did some serious outside the box thinking with their pseudo-SLC mode. Internal data paths are effectively twice as wide as they need to be, writing a cell probably takes a bit less time, buffers are effectively doubled, and reads are probably less error prone too. All this for losing half the capacity, something most enthusiasts would gladly give up for a massive speed gain. Simple and brilliant, all from a bit of firmware coding.S|A

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Charlie Demerjian

Roving engine of chaos and snide remarks at SemiAccurate
Charlie Demerjian is the founder of Stone Arch Networking Services and SemiAccurate.com. SemiAccurate.com is a technology news site; addressing hardware design, software selection, customization, securing and maintenance, with over one million views per month. He is a technologist and analyst specializing in semiconductors, system and network architecture. As head writer of SemiAccurate.com, he regularly advises writers, analysts, and industry executives on technical matters and long lead industry trends. Charlie is also a council member with Gerson Lehman Group. FullyAccurate