What's 120 billion Yen between friends? That's the amount Toshiba wants from Western Digital for meddling with the sale of its flash manufacturing business. Toshiba opened a separate legal action on its home turf of Japan, claiming Western Digital Corp violated the Unfair Competition Prevention Act, among others. Meanwhile, WDC has a motion moving through the court system in California asking for an injunction to keep Toshiba from selling a portion of the joint venture business that manufactures flash for the two companies.
Feelings must be hurt, and that could be why Toshiba announced 4-bit per cell BiCS FLASH recently and why Western Digital issued a separate announcement for 96-layer BiCS FLASH (Gen 4). Normally, both companies announce the same product at the same time and just change the logo along with a quote or two.
4-bit Per Cell OLC Flash
Let's start with quadruple-level cell (QLC) BiCS FLASH first. A number of news outlets posted about the coming QLC SSDs as if this is the next alternative to TLC for your desktop. That's not the case. QLC NAND increases the charge level to sixteen, double that of 3-bit per cell (TLC) NAND. The technology will require the most advanced monitoring and error correction control algorithms built for NAND flash. Even then, QLC will have only between 100 and 150 program erase cycles (est.). In contrast, 3D TLC from Toshiba has between 1,500 and 3,000 PE cycles before ECC technology like LDPC extends the endurance.
QLC will have a limited role that most users will never actually see. The technology will ship in low-power SSDs that focus on write once, read many (WORM) tasks. Facebook and other data center customers have asked for the technology to replace spinning media. At Flash Memory Summit last August, Toshiba laid out the plans for QLC with 2.5" form factor SSDs delivering 100TB of data capacity each.
QLC will eventually make its way to the desktop, but the time frame is still far enough out that we hesitate to make any projections. For example, we kept hearing about TLC for five years before the technology crept in. Once available, it took a few years to become the standard for consumer SSDs--a transition that's currently underway.
Toshiba said the new QLC began shipping to SSD controller designers in early June. Each die holds 768Gbits (96GB) in a 64-layer stack.
96-Layer BiCS FLASH
The Toshiba XG5 SSD is the first to arrive with new 64-layer 3D TLC from Toshiba. The Western Digital announcement stated that the company has built a 96-layer 256Gbit prototype. BiCS3, the version shipping in the XG5, comes in two capacity sizes (256Gbit and 512Gbit). BiCS4 is a technological achievement, but only if the physical die size is smaller than shipping 64-layer.
"Our successful development of the industry's first 96-layer 3D NAND technology demonstrates Western Digital's continued leadership in NAND flash and solid execution to our technology roadmap," said Dr. Siva Sivaram, executive vice president of memory technology at Western Digital. "BiCS4 will be available in 3-bits-per-cell and 4-bits-per-cell architectures, and it contains technology and manufacturing innovations to provide the highest 3D NAND storage capacity, performance and reliability at an attractive cost for our customers. Western Digital's 3D NAND portfolio is designed to address the full range of end markets spanning consumer, mobile, computing and data center."
Western Digital went on to say that BiCS4 will sample to customers in the second half of 2017, and volume manufacturing should begin in 2018.
Both Toshiba and Western Digital plan to present more data about the new achievements at Flash Memory Summit in August.