Western Digital Announces Four Bit Per Cell 64-Layer 3D NAND Flash
by Billy Tallis on July 25, 2017 8:00 AM EST
Western Digital's SanDisk subsidiary and Toshiba have a long history of jointly developing and manufacturing NAND flash memory. While that relationship has been strained by Toshiba's recent financial troubles and attempts to sell of their share of the memory business, the companies are continuing to develop new flash memory technology and are still taking turns making new announcements. In recent months both companies have started sampling SSDs using their 64-layer BiCS3 TLC 3D NAND and have announced that their next generation BiCS4 3D NAND will be a 96-layer design.
Yesterday Western Digital made a small announcement about their other main strategy for increasing density: storing more bits per memory cell. Western Digital will introduce four bit per cell QLC parts built on their 64-layer BiCS3 process, with a capacity of 768Gb (96GB) per die. This is a substantial increase over the 512Gb BiCS3 TLC parts that will be hitting the market soon, and represents not only an increase in in bits stored per memory cell but an increase in the overall size of the memory array. These new 3D QLC NAND parts are clearly intended to offer the best price per GB that Western Digital can manage, but Western Digital claims performance will still be close to that of their 3D TLC NAND. Western Digital's announcement did not mention write endurance, but Toshiba's earlier announcement of 3D QLC NAND claimed endurance of 1000 program/erase cycles, far higher than industry expectations of 100-150 P/E cycles for 3D QLC and comparable to 3D TLC NAND.
Western Digital has not announced any specific products based on QLC NAND flash, but they will be exhibiting both removable media and SSDs using QLC NAND at Flash Memory Summit August 8-10. Western Digital's CTO will be delivering a keynote presentation at FMS on August 8, so more details are likely to be revealed in two weeks.
Western Digital's roadmaps also include plans for QLC parts on their 96-layer BiCS4 process, with capacities up to 1Tb (128GB) per die. BiCS4 production is scheduled to ramp up over 2018 and 2019 with the QLC parts expected to arrive later in the cycle, so Western Digital's first-generation 3D QLC based on the BiCS3 process will probably be their highest-density flash memory in mass production for over a year.
Source: Western Digital
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DanNeely - Tuesday, July 25, 2017 - link
I'm really curious what the max write numbers for these are going to be. Back in the 2d era we saw predictions as low as only a few dozen writes/cell. OTOH enterprise MLC had max write numbers much higher than consumer MLC, so there clearly was some room to push it (presumably at the cost of making it more expensive); and 3d NAND has much larger cell sizes and should be better than high density planar NAND.bill.rookard - Tuesday, July 25, 2017 - link
That's what I thought as well. I know that the physics involved with the tiny (sub 20nm) process made it difficult to keep a decent endurance, but the switch to 3D NAND allowed a large process (40nm) and still allow for higher capacities. And the larger process allowed for better endurance, so it was a win-win.Unless they've done something rather foolish and scaled the process BACK down into the sub 20nm process with the 3D NAND. I get it - capacity is important. But when a company can stuff 20TB into a 3.5" drive using MLC NAND, I don't see that as a problem. Heck, half the 512GB drives only utilize one side of a half-board inside a 2.5" drive.
MrSpadge - Tuesday, July 25, 2017 - link
They're not primarily pushing for finer chips to physically shrink them, but to reduce the cost per bit. with 3D NAND they ARE also pushing towards smaller cell sizes, as it helps again. But so far scaling the numbers of layers is cheaper, so they're focussing on that for now. But eventually the cells will get smaller again.Personally I think this is no problem. Enterprise has it under control (just pay more and get the high endurance stuff) whereas consumers generally don't need huge write endurance numbers. And endurance in terms of TBW or PBW scales with capacity. I.e. you can write more to a 4 TB TLC drive than to a 128 GB MLC drive (ballpark estimate), despite the lower endurance of each cell.
Rocket321 - Tuesday, July 25, 2017 - link
I'm looking forward to a review of a consumer unit in the coming year to see if it can actually hold up to the rated endurance. I find it hard to believe it will last 1,000 P/E cycles.Hurr Durr - Tuesday, July 25, 2017 - link
So, another reason not to buy WD Green, okay.name99 - Tuesday, July 25, 2017 - link
I've been seeing these complaints about how THIS ROUND of flash has unacceptable rewrite capabilities since flash first became known to the public, in the early 2000s.I expect at some point it might even become true, but right now I'm rather more inclined to trust engineers who know something about error correction codes and the properties of their devices over J Random "I'm scared of change, any change, but I mask my fear as 'cautious concern'" Internet User.
"OMG flash is about to fail" ranks up there with
"I have no use for this faster WiFi standard" and
"this new cellular standard means I can use up my data cap in 5 seconds" and
"no replaceable battery/SD card/3.5" jack/DRAM/CD-ROM drive/floppy drive/printer port -- no buy"
as rants that, believe me, no-one is interested in hearing.
Hurr Durr - Wednesday, July 26, 2017 - link
Oh so typical. What makes you think anybody here is interested in another port reductionism worship sermon from a crapple zombie?shabby - Wednesday, July 26, 2017 - link
Buy i needs the printer port...shabby - Wednesday, July 26, 2017 - link
ButZeDestructor - Wednesday, July 26, 2017 - link
"this new cellular standard means I can use up my data cap in 5 seconds"To be fair, in places like Australia where there's both 1gbit LTE and <5GiB data caps on the same network, it's a valid point to make.