Micro Advantage

<div>SK hynix Announces 238 Layer NAND – Mass Production To Start In H1’2023</div>

As the 2022 Flash Memory Summit continues, SK hynix is the latest vendor to announce their next generation of NAND flash memory at the show. Showcasing for the first time the company’s forthcoming 238 layer TLC NAND, which promises both improved density/capacity and improved bandwidth. At 238 layers, SK hynix has, at least for the moment, secured bragging rights for the greatest number of layers in a TLC NAND die – though with mass production not set to begin until 2023, it’s going to be a while until the company’s newest NAND shows up in retail products.

Following closely on the heels of Micron’s 232L TLC NAND announcement last week, SK hynix is upping the ante ever so slightly with a 238 layer design. Though the difference in layer counts is largely inconsequential when you’re talking about NAND dies with 200+ layers to begin with, in the highly competitive flash memory industry it gives SK hynix bragging rights on layer counts, breaking the previous stalemate between them, Samsung, and Micron at 176L.

From a technical perspective, SK hynix’s 238L NAND further builds upon the basic design of their 176L NAND. So we’re once again looking at a string stacked design, with SH hynix using a pair of 119 layer decks, up from 88 layers in the previous generation. This makes SK hynix the third flash memory vendor to master building decks over 100 layers tall, and is what’s enabling them to produce a 238L NAND design that holds the line at two decks.

SK hynix’s NAND decks continue to be built with their charge-trap, CMOS under Array (CuA) architecture, which sees the bulk of the NAND’s logic placed under the NAND memory cells. According to the company, their initial 512Gbit TLC part has a die size of 35.58mm2, which works out to a density of roughly 14.39 Gbit/mm2. That’s a 35% improvement in density over their previous-generation 176L TLC NAND die at equivalent capacities. Notably, this does mean that SK hynix will be ever so slightly trailing Micron’s 232L NAND despite their total layer count advantage, as Micron claims they’ve hit a density of 14.6 Gbit/mm2 on their 1Tbit dies.

SK hynix 3D TLC NAND Flash Memory
  238L 176L
Layers 238 176
Decks 2 (x119) 2 (x88)
Die Capacity 512 Gbit 512 Gbit
Die Size (mm2) 35.58mm2 ~47.4mm2
Density (Gbit/mm2) ~14.39 10.8
I/O Speed 2.4 MT/s
(ONFi 5.0)
1.6 MT/s
(ONFI 4.2)
CuA / PuC Yes Yes

Speaking of 1Tbit, unlike Micron, SK hynix is not using the density improvements to build higher capacity dies – at least, not yet. While the company has announced that they will be building 1Tbit dies next year using their 238L process, for now they’re holding at 512Gbit, the same capacity as their previous generation. So all other factors held equal, we shouldn’t expect the first wave drives built using 238L NAND to have any greater capacity than the current generation. But, if nothing else, at least SK hynix’s initial 238L dies are quite small – though whether that translates at all to smaller packages remains to be seen.

Besides density improvements, SK hynix has also improved the performance and power consumption of their NAND. Like the other NAND vendors, SK hynix is using this upcoming generation of NAND to introduce ONFi 5.0 support. ONFi 5.0 is notable for not only increasing the top transfer rate to 2400MT/second – a 50% improvement over ONFi 4.2 – but it also introduces a new NV-LPDDR4 signaling method. As it’s based on LPDDR signaling (unlike the DDR3-derrived mode in ONFi 4.x), NV-LPDDR4 offers tangible reductions in the amount of power consumed by NAND signaling. SK hynix isn’t breaking their power consumption figures out to this level of detail, but for overall power consumption, they’re touting a 21% reduction in energy consumed for read operations. Presumably this is per bit, so it will be counterbalanced by the 50% improvement in bandwidth.

This week’s announcement comes as SK hynix has begun shipping samples of the 238L NAND to their customers. As previously mentioned, the company is not planning on kicking off mass production until H1’2023, so it will be some time before we see the new NAND show up in retail products. According to SK hynix, their plan is to start with shipping NAND for consumer SSDs, followed by smartphones and high-capacity server SSDs. That, in turn, will be followed up with the introduction of 1Tbit 238L NAND later in 2023.

Solidigm Announces P41 Plus SSD: Taking Another Shot at QLC With Cache Tiering

Although Intel is no longer directly in the SSD market these days, their SSD team and related technologies continue to live on under the SK hynix umbrella as Solidigm. Since their initial formation at the very end of 2021, Solidigm has been in the process of reestablishing their footing, continuing to sell and support Intel’s previous SSD portfolio while continuing development of their next generation of SSDs. On the enterprise side of matters this recently culminated in the launch of their new D7 SSDs. Meanwhile on the consumer side of matters, today at Flash Memory Summit the company is announcing their first post-Intel consumer SSD, the Solidigm P41 Plus

The P41 Plus is, at a high level, the successor to Intel’s 670p SSD, the company’s second-generation QLC-based SSD. And based on that description alone, a third generation QLC drive from Solidigm is something that few AnandTech readers would find remarkable. QLC makes for cheap high(ish) capacity SSDs, which OEMs love, while computing enthusiasts are decidedly less enthusiastic about them.

But then the P41 Plus isn’t just a traditional QLC drive.

One of the more interesting ventures out of Intel’s time as a client SSD manufacturer was the company’s forays into cache tiering. Whether it was using flash memory as a hard drive cache, using 3D XPoint as a hard drive cache, or even using 3D XPoint as a flash memory cache, Intel tried several ways to speed up the performance of slower storage devices in a cost-effective manner. And while Intel’s specific solutions never really caught on, Intel’s core belief that some kind of caching is necessary proved correct, as all modern TLC and QLC SSDs come with pseudo-SLC caches for improved burst write performance.

While they are divorced from Intel these days, Solidigm is picking up right where Intel left off, continuing to experiment with cache tiering. Coming from the same group that developed Intel’s mixed 3D XPoint/QLC drives such as the Optane Memory H20, Solidigm no longer has access to Intel’s 3D XPoint memory (and soon, neither will Intel). But they do have access to flash memory. So for their first solo consumer drive as a stand-alone subsidiary, Solidigm is taking a fresh stab at cache tiering, expanding the role of the pSLC cache to serve as both a write cache and a read cache.