Wccftech reports that Micron plans to "introduce" NAND with 8 bits (1 byte) per cell:
Back in May of 2018, Micron introduced Quad-Level (QLC) NAND tech and, surprisingly, saw their stock tumble to pricing levels of ~$30 down from ~$60. This was the result of complex NAND pricing and supply/demand factors, not just the introduction of QLC, to be clear. I have just confirmed from multiple sources and stakeholders that Micron is intending to introduce their Octa-Level (OLC) NAND either in Q1 or latest by Q2 2019.
OLC NAND would have 28 (256) states and 28-1 (255) threshold voltages, compared to just 16 states for today's QLC NAND.
3D QLC NAND SSDs arrived on the market in 2018. QLC NAND has lower write endurance, estimated at 1,000 program/erase (PE) cycles, compared to 3,000 P/E cycles for triple-level cell (TLC) NAND, 10,000 P/E cycles for multi-level cell (MLC) NAND, and 100,000 P/E cycles for single-level cell NAND. This exceeds previous expectations of 1,000 P/E cycles for TLC NAND and 100 cycles for QLC NAND. Intel's SSD 660p drives using QLC NAND are rated for only about 0.1 drive writes per day for 5 years, or about 200 TB written on a 1 TB drive. Data retention is also reduced.
In 2013, it was reported that the U.S. Intelligence Advanced Research Projects Activity (IARPA) funded Crocus Technology development of 8-bits-per-cell Magnetic Logic Unit (MLU) memory, which would use two 4-bit layers:
Douglas Lee, VP for system strategy and corporate product development at Crocus, pointed out NAND and MRAM bits-per-cell limitations: "The current semiconductor non-volatile memory state-of-the-art is 3-4 bits per cell, as achieved in NAND flash memory, and is reaching the physical limits of floating gate memory technology. The current state-of-the-art in MRAM is only 1 bit per cell storage."
(Score: 0) by Anonymous Coward on Saturday February 09 2019, @11:13PM (3 children)
I'm not sure the read/write speeds would drop - TLC is faster than S/MLC. By the time this comes to market it probably will be too. The real concern is endurance like you've said, a few Mb/s read/write either way isn't such a big concern when that's very rarely a bottleneck anymore.
(Score: 3, Informative) by takyon on Saturday February 09 2019, @11:34PM (2 children)
https://www.speedguide.net/faq/slc-mlc-or-tlc-nand-for-solid-state-drives-406 [speedguide.net]
https://www.anandtech.com/show/5067/understanding-tlc-nand/2 [anandtech.com]
https://en.wikipedia.org/wiki/Multi-level_cell [wikipedia.org]
Before you take into account possible differences between the use of 3D layers, over provisioning, controller, MLC/SLC mode, etc., TLC is slower than MLC/SLC. QLC is slower than TLC, etc.
For example, Intel SSD 660p is a QLC NAND drive. It starts out with decent performance but when you fill up the SLC cache, the performance plummets:
https://images.anandtech.com/graphs/graph13078/sustained-sw-eff.png [anandtech.com]
[SIG] 10/28/2017: Soylent Upgrade v14 [soylentnews.org]
(Score: 0) by Anonymous Coward on Sunday February 10 2019, @02:48AM (1 child)
You linked to one about MB/s vs watt. Speed ones:
https://images.anandtech.com/graphs/graph13078/burst-sw.png [anandtech.com]
https://images.anandtech.com/graphs/graph13078/sustained-sw.png [anandtech.com]
The issue seems to be about "queue depth" (requests at the same time, "shared access"). QD1 shows similar speed full or empty. But if really above cache size... it should not matter how many requests.
See article page https://www.anandtech.com/show/13078/the-intel-ssd-660p-ssd-review-qlc-nand-arrives/6 [anandtech.com] , maybe someone can find the catch.
(Score: 2) by takyon on Sunday February 10 2019, @03:27AM
Here's a better link:
https://www.anandtech.com/show/13512/the-crucial-p1-1tb-ssd-review/7 [anandtech.com]
Scroll down to "Whole-Drive Fill".
You can see that the (QLC) drive starts at around 1600 MB/s, but then plummets to around 100 MB/s for most off the time after SLC cache is filled.
Use the dropdown to select the Intel SSD 660p and it shows a similar behavior.
TLC is slower than S/MLC, and QLC is slower than TLC. The 100+ GB SLC cache in those two drives compensate for that, and it gets gradually emptied so you don't notice QLC's slowness unless you are writing hundreds of gigabytes at once.
[SIG] 10/28/2017: Soylent Upgrade v14 [soylentnews.org]