Migrating from mDOC: Options, Challenges and Benefits

DiskOnChip is a well-known line of flash memory products created by M-Systems (now SanDisk). First introduced in 1994, DiskOnChip (also called mDOC) became very popular in embedded applications because of its simple integration and strong performance. As a result, mDOC was quickly adopted by embedded device makers, in spite of the fact that it was more expensive than raw flash chips. Key to the product’s easy integration was TrueFFS, M System’s device driver which made mDOC appear as a block device, able to be formatted using any file system. TrueFFS performed functions of wear leveling and bad block management whereas the ECC (Error Correction Codes) were handled in hardware by mDOC’s controller. Most mainstream embedded operating systems were supported by mDOC, with Windows and Linux being two of the most popular. Unlike raw flash parts, which are made by several manufacturers, M-Systems (and later SanDisk) was the sole supplier of mDOC.

Recently, SanDisk announced end-of-life (EOL) for several parts in the mDOC product line. Customers who were using these parts were asked to place their final order and transition to a different storage technology. Usually when a flash part is EOL’d by one manufacturer, customers can source a compatible flash part from another manufacturer. This involves changing software configuration and driver support, but does not typically require a redesign of hardware. However, since SanDisk was the sole source for mDOC parts, many customers had to redesign their entire system. Faced with mounting redesign costs, customers of the EOL’d mDOC parts found themselves in a very difficult situation.