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Kioxia Details BiCS 8 NAND at FMS 2024: 218 Layers With Superior Scaling
Kioxia's booth at FMS 2024 was a busy one with multiple technology demonstrations keeping visitors occupied. A walk-through of the BiCS 8 manufacturing process was the first to grab my attention. Kioxia and Western Digital announced the sampling of BiCS 8 in March 2023. We had touched briefly upon its CMOS Bonded Array (CBA) scheme in our coverage of Kioxial's 2Tb QLC NAND device and coverage of Western Digital's 128 TB QLC enterprise SSD proof-of-concept demonstration. At Kioxia's booth, we got more insights.

Traditionally, fabrication of flash chips involved placement of the associate logic circuitry (CMOS process) around the periphery of the flash array. The process then moved on to putting the CMOS under the cell array, but the wafer development process was serialized with the CMOS logic getting fabricated first followed by the cell array on top. However, this has some challenges because the cell array requires a high-temperature processing step to ensure higher reliability that can be detrimental to the health of the CMOS logic. Thanks to recent advancements in wafer bonding techniques, the new CBA process allows the CMOS wafer and cell array wafer to be processed independently in parallel and then pieced together, as shown in the models above.

The BiCS 8 3D NAND incorporates 218 layers, compared to 112 layers in BiCS 5 and 162 layers in BiCS 6. The company decided to skip over BiCS 7 (or, rather, it was probably a short-lived generation meant as an internal test vehicle). The generation retains the four-plane charge trap structure of BiCS 6. In its TLC avatar, it is available as a 1 Tbit device. The QLC version is available in two capacities - 1 Tbit and 2 Tbit.

Kioxia also noted that while the number of layers (218) doesn't compare favorably with the latest layer counts from the competition, its lateral scaling / cell shrinkage has enabled it to be competitive in terms of bit density as well as operating speeds (3200 MT/s). For reference, the latest shipping NAND from Micron - the G9 - has 276 layers with a bit density in TLC mode of 21 Gbit/mm², and operates at up to 3600 MT/s. However, its 232L NAND operates only up to 2400 MT/s and has a bit density of 14.6 Gbit/mm².

It must be noted that the CBA hybrid bonding process has advantages over the current processes used by other vendors - including Micron's CMOS under array (CuA) and SK hynix's 4D PUC (periphery-under-chip) developed in the late 2010s. It is expected that other NAND vendors will also move eventually to some variant of the hybrid bonding scheme used by Kioxia.

Storage

March 30, 2025

Kioxia Details BiCS 8 NAND at FMS 2024: 218 Layers With Superior Scaling
Kioxia's booth at FMS 2024 was a busy one with multiple technology demonstrations keeping visitors occupied. A walk-through of the BiCS 8 manufacturing process was the first to grab my attention. Kioxia and Western Digital announced the sampling of BiCS 8 in March 2023. We had touched briefly upon its CMOS Bonded Array (CBA) scheme in our coverage of Kioxial's 2Tb QLC NAND device and coverage of Western Digital's 128 TB QLC enterprise SSD proof-of-concept demonstration. At Kioxia's booth, we got more insights.

Traditionally, fabrication of flash chips involved placement of the associate logic circuitry (CMOS process) around the periphery of the flash array. The process then moved on to putting the CMOS under the cell array, but the wafer development process was serialized with the CMOS logic getting fabricated first followed by the cell array on top. However, this has some challenges because the cell array requires a high-temperature processing step to ensure higher reliability that can be detrimental to the health of the CMOS logic. Thanks to recent advancements in wafer bonding techniques, the new CBA process allows the CMOS wafer and cell array wafer to be processed independently in parallel and then pieced together, as shown in the models above.

The BiCS 8 3D NAND incorporates 218 layers, compared to 112 layers in BiCS 5 and 162 layers in BiCS 6. The company decided to skip over BiCS 7 (or, rather, it was probably a short-lived generation meant as an internal test vehicle). The generation retains the four-plane charge trap structure of BiCS 6. In its TLC avatar, it is available as a 1 Tbit device. The QLC version is available in two capacities - 1 Tbit and 2 Tbit.

Kioxia also noted that while the number of layers (218) doesn't compare favorably with the latest layer counts from the competition, its lateral scaling / cell shrinkage has enabled it to be competitive in terms of bit density as well as operating speeds (3200 MT/s). For reference, the latest shipping NAND from Micron - the G9 - has 276 layers with a bit density in TLC mode of 21 Gbit/mm², and operates at up to 3600 MT/s. However, its 232L NAND operates only up to 2400 MT/s and has a bit density of 14.6 Gbit/mm².

It must be noted that the CBA hybrid bonding process has advantages over the current processes used by other vendors - including Micron's CMOS under array (CuA) and SK hynix's 4D PUC (periphery-under-chip) developed in the late 2010s. It is expected that other NAND vendors will also move eventually to some variant of the hybrid bonding scheme used by Kioxia.

Storage

March 30, 2025

Samsung's 128 TB-Class BM1743 Enterprise SSD Displayed at FMS 2024
Samsung had quietly launched its BM1743 enterprise QLC SSD last month with a hefty 61.44 TB SKU. At FMS 2024, the company had the even larger 122.88 TB version of that SSD on display, alongside a few recorded benchmarking sessions. Compared to the previous generation, the BM1743 comes with a 4.1x improvement in I/O performance, improvement in data retention, and a 45% improvement in power efficiency for sequential writes.

The 128 TB-class QLC SSD boasts of sequential read speeds of 7.5 GBps and write speeds of 3 GBps. Random reads come in at 1.6 M IOPS, while 16 KB random writes clock in at 45K IOPS. Based on the quoted random write access granularity, it appears that Samsung is using a 16 KB indirection unit (IU) to optimize flash management. This is similar to the strategy adopted by Solidigm with IUs larger than 4K in their high-capacity SSDs.

A recorded benchmark session on the company's PM9D3a 8-channel Gen 5 SSD was also on display.

The SSD family is being promoted as a mainstream option for datacenters, and boasts of sequential reads up to 12 GBps and writes up to 6.8 GBps. Random reads clock in at 2 M IOPS, and random writes at 400 K IOPS.

Available in multiple form-factors up to 32 TB (M.2 tops out at 2 TB), the drive's firmware includes optional support for flexible data placement (FDP) to help address the write amplification aspect.

The PM1753 is the current enterprise SSD flagship in Samsung's lineup. With support for 16 NAND channels and capacities up to 32 TB, this U.2 / E3.S SSD has advertised sequential read and write speeds of 14.8 GBps and 11 GBps respectively. Random reads and writes for 4 KB accesses are listed at 3.4 M and 600 K IOPS.

Samsung claims a 1.7x performance improvement and a 1.7x power efficiency improvement over the previous generation (PM1743), making this TLC SSD suitable for AI servers.

The 9^th Gen. V-NAND wafer was also available for viewing, though photography was prohibited. Mass production of this flash memory began in April 2024.

Storage

March 24, 2025

Kioxia Demonstrates RAID Offload Scheme for NVMe Drives
At FMS 2024, Kioxia had a proof-of-concept demonstration of their proposed a new RAID offload methodology for enterprise SSDs. The impetus for this is quite clear: as SSDs get faster in each generation, RAID arrays have a major problem of maintaining (and scaling up) performance. Even in cases where the RAID operations are handled by a dedicated RAID card, a simple write request in, say, a RAID 5 array would involve two reads and two writes to different drives. In cases where there is no hardware acceleration, the data from the reads needs to travel all the way back to the CPU and main memory for further processing before the writes can be done.

Kioxia has proposed the use of the PCIe direct memory access feature along with the SSD controller's controller memory buffer (CMB) to avoid the movement of data up to the CPU and back. The required parity computation is done by an accelerator block resident within the SSD controller.

In Kioxia's PoC implementation, the DMA engine can access the entire host address space (including the peer SSD's BAR-mapped CMB), allowing it to receive and transfer data as required from neighboring SSDs on the bus. Kioxia noted that their offload PoC saw close to 50% reduction in CPU utilization and upwards of 90% reduction in system DRAM utilization compared to software RAID done on the CPU. The proposed offload scheme can also handle scrubbing operations without taking up the host CPU cycles for the parity computation task.

Kioxia has already taken steps to contribute these features to the NVM Express working group. If accepted, the proposed offload scheme will be part of a standard that could become widely available across multiple SSD vendors.

Storage

March 28, 2025

Intel Sells Its Arm Shares, Reduces Stakes in Other Companies
Intel has divested its entire stake in Arm Holdings during the second quarter, raising approximately $147 million. Alongside this, Intel sold its stake in cybersecurity firm ZeroFox and reduced its holdings in Astera Labs, all as part of a broader effort to manage costs and recover cash amid significant financial challenges.

The sale of Intel's 1.18 million shares in Arm Holdings, as reported in a recent SEC filing, comes at a time when the company is struggling with substantial financial losses. Despite the $147 million generated from the sale, Intel reported a $120 million net loss on its equity investments for the quarter, which is a part of a larger $1.6 billion loss that Intel faced during this period.

In addition to selling its stake in Arm, Intel also exited its investment in ZeroFox and reduced its involvement with Astera Labs, a company known for developing connectivity platforms for enterprise hardware. These moves are in line with Intel's strategy to reduce costs and stabilize its financial position as it faces ongoing market challenges.

Despite the divestment, Intel's past investment in Arm was likely driven by strategic considerations. Arm Holdings is a significant force in the semiconductor industry, with its designs powering most mobile devices, and, for obvious reasons, Intel would like to address these. Intel and Arm are also collaborating on datacenter platforms tailored for Intel's 18A process technology. Additionally, Arm might view Intel as a potential licensee for its technologies and a valuable partner for other companies that license Arm's designs.

Intel's investment in Astera Labs was also a strategic one as the company probably wanted to secure steady supply of smart retimers, smart cable modems, and CXL memory controller, which are used in volumes in datacenters and Intel is certainly interested in selling as many datacenter CPUs as possible.

Intel's financial struggles were highlighted earlier this month when the company released a disappointing earnings report, which led to a 33% drop in its stock value, erasing billions of dollars of capitalization. To counter these difficulties, Intel announced plans to cut 15,000 jobs and implement other expense reductions. The company has also suspended its dividend, signaling the depth of its efforts to conserve cash and focus on recovery. When it comes to divestment of Arm stock, the need for immediate financial stabilization has presumably taken precedence, leading to the decision.

CPUs

March 24, 2025

Kioxia Details BiCS 8 NAND at FMS 2024: 218 Layers With Superior Scaling
Kioxia's booth at FMS 2024 was a busy one with multiple technology demonstrations keeping visitors occupied. A walk-through of the BiCS 8 manufacturing process was the first to grab my attention. Kioxia and Western Digital announced the sampling of BiCS 8 in March 2023. We had touched briefly upon its CMOS Bonded Array (CBA) scheme in our coverage of Kioxial's 2Tb QLC NAND device and coverage of Western Digital's 128 TB QLC enterprise SSD proof-of-concept demonstration. At Kioxia's booth, we got more insights.

Traditionally, fabrication of flash chips involved placement of the associate logic circuitry (CMOS process) around the periphery of the flash array. The process then moved on to putting the CMOS under the cell array, but the wafer development process was serialized with the CMOS logic getting fabricated first followed by the cell array on top. However, this has some challenges because the cell array requires a high-temperature processing step to ensure higher reliability that can be detrimental to the health of the CMOS logic. Thanks to recent advancements in wafer bonding techniques, the new CBA process allows the CMOS wafer and cell array wafer to be processed independently in parallel and then pieced together, as shown in the models above.

The BiCS 8 3D NAND incorporates 218 layers, compared to 112 layers in BiCS 5 and 162 layers in BiCS 6. The company decided to skip over BiCS 7 (or, rather, it was probably a short-lived generation meant as an internal test vehicle). The generation retains the four-plane charge trap structure of BiCS 6. In its TLC avatar, it is available as a 1 Tbit device. The QLC version is available in two capacities - 1 Tbit and 2 Tbit.

Kioxia also noted that while the number of layers (218) doesn't compare favorably with the latest layer counts from the competition, its lateral scaling / cell shrinkage has enabled it to be competitive in terms of bit density as well as operating speeds (3200 MT/s). For reference, the latest shipping NAND from Micron - the G9 - has 276 layers with a bit density in TLC mode of 21 Gbit/mm², and operates at up to 3600 MT/s. However, its 232L NAND operates only up to 2400 MT/s and has a bit density of 14.6 Gbit/mm².

It must be noted that the CBA hybrid bonding process has advantages over the current processes used by other vendors - including Micron's CMOS under array (CuA) and SK hynix's 4D PUC (periphery-under-chip) developed in the late 2010s. It is expected that other NAND vendors will also move eventually to some variant of the hybrid bonding scheme used by Kioxia.

Storage

March 30, 2025