For starters, the BG4 uses 96-layer 3D BiCS TLC NAND instead of 64-layers, which not only bolsters overall capacities, but also keeps power consumption in check (Toshiba says that overall power consumption has been reduced by 20 percent). And whereas the BG3 uses an NVMe PCIe 3.0 x2 interface, the BG4 instead uses an NVMe PCIe 3.0x4 interface for increased throughput.
So, what does this mean for shipping parts? Maximum capacity for SSDs has doubled from 512GB for the BG3 to 1TB for the BG4. Performance numbers -- through the combination of the 96-layer design and NVMe PCIe 3.0x4 interface upgrade -- means that performance has increased dramatically.
Sequential reads and writes have jumped from 1,500MB/s and 1,000MB/sec respectively to 2,250MB/s and 1,700MB/s representing gains of 50 percent and 70 percent. Likewise, random read/write IOPS have ballooned from 150,000 and 100,000 respectively to 380,000 and 190,000. For those keeping score, that's a 153 percent improvement for random read IOPS alone. We should note that the SSDs don't include DRAM onboard and instead make use of the Host Memory Buffer (HMB) feature to cache from system RAM.
Toshiba offers the BG4 in one of two form-factors: it comes in a M.2 1620 BGA form-factor that can be surface-mounted onto a board or in a standard M.2 2230 removable module.
Toshiba will ship the BG4 in 128GB, 256GB, 512GB and 1TB capacities, and they are all currently sampling to customers. However, we should expect general availability in new systems starting in Q2. Since these SSDs are aimed at OEMs instead of consumers, we don't have any guidance on pricing, but Toshiba is looking to match the capacity of SATA SSDs while offering far superior performance at the same price.