Despite Toshiba's troubles with regulatory agencies, bankers, governments, and partner Western Digital, the company has a new advanced flash poised to change the storage landscape. For the last year, analysts have placed the NAND market's recovery on the shoulders of Toshiba's BiCS flash production. IMFT, Samsung, and Sk Hynix play a role, but Toshiba is the linchpin because 3D BiCS is the uncertain piece of the puzzle.
Toshiba originally said to expect BiCS in Q3 2017, essentially now, but many analysts predicted we wouldn't see volume production until early 2018. Most of the speculation stems from Toshiba's financial troubles that are leading to the sale, in whole or in part, of its flash manufacturing outfit. Analyst predictions are valuable to us, but only in context. Both Toshiba and partner Western Digital have announced products with third generation 3D NAND, but neither company has products in retail. We can now say that BiCS-powered SSDs are coming and we won't have to wait until 2018.
The new flash utilizes 64 stacked layers and comes in 256Gbit (32GB) and 512Gbit (64GB) die, but vendors will use different die for different applications. SSD's are fast because they read and write to several die simultaneously in a RAID array-like arrangement. Large and small die capacities are nothing new, but as NAND technology progresses, the vendors increasingly use targeted sizes for different applications. Low capacity models use the smaller die for increased parallelization, which boosts performance, while larger die are used for SSDs with more capacity.
Without the larger die, though, controller technology becomes very expensive because the controller has to address more die simultaneously. That adds traces, more complex algorithms, and requires more processing power in the form of higher clock speeds and faster processors. In most cases, the larger die will drop right in and the same controller can take advantage of the extra capacity without a significant redesign. At that point, the high capacity products hinge on the amount of DRAM the controller can address to cache the LBA map.
The XG5 is the first SSD featuring Toshiba's new BiCS flash. It's an OEM model that follows the XG3 and XG4 OEM NVMe SSDs. Toshiba doesn't disclose design wins, but we know Dell, MSI, and other high-performance notebooks used the XG series through 2016 and 2017. Toshiba displayed the new XG5 model at Dell World just days prior to Computex, so we assume Dell will use the drive in back-to-school models this year. We're also told OCZ will use the XG5 as the base for the next generation RD series.
There were subtle differences between the OEM XG3 and retail RD400. OCZ tuned the RD400 for enthusiasts and included a custom NVMe driver for Windows. The driver makes a big difference. Some OEMs provide custom drivers, but the base XG5 we're testing today uses the standard Windows 10 NVMe driver. Some features are not optimized with the standard driver, so the XG5 performance you see today should only be used as a reference point for the next OCZ RD product.
OEM partners will purchase the XG5 in three capacities that range from 256GB to 1TB. All drives in this series use the M.2 2280 single-sided form factor. Toshiba is coy about the XG5's specifications because ultimately the performance of final products varies by OEM. Performance is also dependent on firmware, which companies can adjust based on their thermal and power requirements. For instance, if a company reduces the 3,000 MB/s sequential read performance to 2,800, it might gain an extra 60 minutes of battery life. Then they could market a model with nine hours of battery life instead of eight.
Toshiba provided sequential performance specifications for the XG5 reference design, but not random performance. The XG5 reference design is capable of 3,000/2,100 MB/s of sequential read/write throughput.
Toshiba isn't sharing information about the new TC58NCP090GSD controller, either. The company has always kept certain aspects of its technology secret. We could never get any solid answers about the controller in the XG3 / RD400. We do know the new controller uses a flip chip design, and that isn't the same design as the XG3. The performance characteristics lead us to believe the controller can utilize at least eight channels. We asked, but our questions went unanswered, again.
The actual die appears to be slightly larger than the Phison E7. The E7 also uses an exposed flip chip design. This led us to believe the two share some digital DNA, but the physical size difference takes that possibility off the table.
The label on our reference design XG5 has a PSID, so this model supports self-encrypting drive (SED) technology. We later found that TCG Opal encryption is an option for OEMs.
Things get interesting on the NAND side. Toshiba and manufacturing partner Western Digital have both stated that 2-bit per cell NAND (MLC) is dead for the consumer market. There will always be a young enterprising company that tries to make a name for itself with a few batches of MLC, but all of the fabs have similar plans for the consumer market.
The Toshiba XG5 will use both BiCS die capacities. It's easy to assume the 256GB model will use the 256Gbit die and the 1TB will use the 512Gbit die. The 512GB model could go either way. Toshiba wouldn't say if it uses the smaller or the larger die. The SSD would be faster with smaller die, but with the larger die it would be cheaper. In time, we'll get one and find out.
Toshiba armed the XG5 1TB reference design with 512Gbit die. The design uses two NAND packages with eight die each. Toshiba can, and eventually will, build 16-die packages. That could lead to a 2TB single-sided XG5 model in the future. If the controller can handle it, we could even see a 4TB model with components on both sides.
Pricing, Warranty & Endurance
We have it on good authority that this is the base for the next OCZ RD-series NVMe SSD, but Toshiba won't sell the XG5 into the channel. The same was also said about the XG3, but several sold as system pulls early in the product life cycle. Now that the XG3 with 15nm planar MLC is end of life, several them are available from different sellers. MyDigitalDiscount has 20,000 XG3 SSDs available in three capacities. The XG3 512GB currently sells for just $200 (Mydigitaldiscount.com) and $219.99 (Amazon). There's a good chance we will see the XG5 sell as a gray market product at some point, as well.
OEMs selling the Toshiba XG5 in pre-built systems will dictate warranty and endurance specifications. Most, if not all, systems don't list specific SSD performance or endurance specifications.
A Closer Look
Sadly, the XG5 doesn't come with the cool sticker used on the promotional images. The drive looks like any standard OEM SSD with a boring white label.
BiCS NAND is the star of this show. There is more to this story than meets the eye. With all consumer SSDs moving over to 3D TLC, the XG5 gives us our first look at what the new definition of "high-performance" is like.
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