Toshiba's ball-grid-array SSDs offer OEMs a tempting blend of low cost, small size, and energy efficiency, but thus far those perks have come at the cost of speed. Historically, the company's BG-series drives skipped onboard DRAM and depended on NVMe's Host Memory Buffer (HMB) feature to offset the performance implications of that omission. However, as we saw when we reviewed the BG3's consumer-facing cousin, the RC100, HMB isn't a perfect substitute for good ol' memory chips. Toshiba acknowledges that fact and consequentially equipped BG3 drives with only a two-lane PCIe link.
That situation seem to be changing with the newest incarnation the series, the BG4. Toshiba claims that firmware improvements let those SSDs use HMB more effectively. Coupled with an upgrade to the latest and greatest 96-layer BiCS NAND, the drive's new tricks should let it hit 2250 MB/s sequential read speeds and 1700 MB/s sequential write speeds. On the random I/O side, the BG4 ought to be capable of hitting 380K read IOPS and 190K write IOPS. So improved are the BG4's transfer rates that Toshiba has finally deemed it time to outfit the drive with a four-lane PCIe link instead of just two.
Like its ancestors, the BG4 comes in a surface-mounted M.2-1620 version as well as a stubby little M.2-2230 stick. There's now a 1-TB version at the top of the lineup, where the BG3 only went up to 512 GB. The new drive has already been sampled to some of Toshiba's OEM partners, and the company expects broader availability in Q2 of this year. Expect to see this guy shipping inside of thin notebooks and embedded systems later in 2019.