4 ms·
In 1991 or so, Intel was speccing devices with 100K erase cycles. In private conversation we were told "Oh, they'll last millions, it's just that erases take lo
by kabdib 7y ago
In 1991 or so, Intel was speccing devices with 100K erase cycles. In private conversation we were told "Oh, they'll last millions, it's just that erases take longer and longer to the point where you run out of patience and just declare the block dead." I don't remember the part sizes, but they were in the low megabit range.
Challenge accepted, I tried to wear a device out (my setup had direct bus access to the flash part in question, no remapping layer). Went for months without an error and I eventually repurposed that corner of my desk.
30 years later, they've pushed the technology a little :-)
You won't get 10K out of an SLC cell (ten years ago those would suffer around 3,000 erase cycles, and it has to be much worse now). I don't know what QLC endurance is (16 voltage levels in a cell, run away), but I wouldn't be surprised if it was a few hundred cycles.
- wtallis 7y ago> You won't get 10K out of an SLC cell (ten years ago those would suffer around 3,000 erase cycles, and it has to be much worse now). 10k P/E cycles is the right ballpark for SLC 3D NAND these days, and it's never been anywhere as low as 3k—that's more like what good TLC 3D NAND gets. QLC is in the 500-1000 cycle range.
- kabdib 7y agoYup, I had mis-remembered the SLC versus TLC numbers. I'm surprised QLC gets as high as 1000, frankly. It's like the cells are on a first-name basis with the electrons they hold.
- wtallis 7y agoI think it was worse with TLC right before the transition to 3D NAND. They were down to about 8 electrons between voltage states. 3D NAND memory cells are physically much larger than 15nm planar NAND, and most are a lot less leaky.
- kabdib 7y agoEIGHT electrons? Indistinguishable from magic, man. [Cue future archeologists: "Remember when our grandparents could only get a few gigabytes on a quark? How primitive, how sooo last-femtocentury."]
- davidcuddeback 7y ago> last-femtocentury You nerd-sniped me. I couldn't resist calculating it. A femtocentury is about 3.16 microseconds.
- wahern 7y agoDoes anybody sell standalone SLC drives these days? I was bummed when Intel stopped selling theirs several years ago.
- wtallis 7y agoSamsung's "Z-NAND" is a latency-optimized 3D SLC NAND, which uses smaller page and block sizes than their capacity-oriented mainstream 3D NAND. The Samsung 983 ZET, SZ983 and SZ985 are drives using that memory. Kioxia (formerly Toshiba) is sampling their version of the same basic idea, and SSDs using that memory should be coming out during the next few months. Intel has of course replaced SLC NAND with their 3D XPoint memory, which is about twice the price but can sustain better write speeds because it doesn't have flash memory's slow block erase operations.