OWC SSDs: SLC Mode Background

Created on: May 25, 2018
Last updated: April 10, 2020


Please note that starting in 2017, many OWC SSDs include a feature known as "SLC Cache Mode." These drives do not contain SLC flash modules. Rather, they contain either MLC or TLC flash modules as well as a flash controller capable of providing a special caching function that allows the MLC and TLC NAND to emulate the performance of SLC NAND. Together, this provides for greater storage capacity than is possible with SLC-based drives, and greater performance than is possible with standard MLC- and TLC-based drives. 

How it Works

The flash controller will use some of the onboard flash memory in "SLC Mode" during write operations, in order to boost write performance. When the flash being used for this purpose is exhausted, the write operations on the drive slow down significantly. When this occurs it is not uncommon to see write speeds around 300MB/s until the flash memory is released and able to be used again.

However, for most day-to-day write operations that do not involve large data sets or data-intensive workflows such as 4K video editing (i.e. situations where the drive write operation occurs for extended periods of time), you should not see the drop in write speeds because the cache will not be exhausted in those scenarios.

SSDs with SLC Mode

  • OWC Mercury Electra 3G and 6G SSDs
    • As of May 25, 2018 the applicable 6G part numbers include: OWCS3D7E6G120 (shipping soon), OWCS3D7E6G250, OWCS3D7E6G500, OWCS3D7E6GT1.0
    • As of May 25, 2018 the applicable 3G part numbers include: OWCS3D7E3G120, OWCS3D7E3G250, OWCS3D7E3G500, OWCS3D7E3GT1.0
  • OWC Aura Pro X 
    • As of May 25, 2018 the part numbers are: OWCS3DAPB4MB02, OWCS3DAPB4MB05, OWCS3DAPB4MB10, OWCS3DAPB4MB20

  • OWC Aura Pro X2

  • OWC Aura N

  • OWC Neptune SSDs
    • As of May 25, 2018 the part numbers are: OWCS3D7N120, OWCS3D7N250, OWCS3D7N500
  • OWC Mercury M.2 SSDs
    • As of May 25, 2018 the part numbers are: OWCS3DAPB4NV02, OWCS3DAPB4NV05, OWCS3DAPB4NV10, OWCS3DAPB4NV20