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Comment by quasse | Hacker News Reader

This is multi-level cell flash memory, and it's been in use for years. Instead of "high" or "low" voltage they use the in-between states to encode more bits per cell. [1]

I worked at an embedded startup when SD cards started switching to MLC and we saw a really notable decrease in storage reliability. We ended up sourcing special SD cards that were flashed with embedded controller firmware restoring them to single level cell functionality. Your storage space is divided by 2^n going from n levels of voltage per cell back to SLC, but we saw greatly increased data integrity.

[1] https://en.wikipedia.org/wiki/Multi-level_cell

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> This is multi-level cell flash memory, and it's been in use for years. Instead of "high" or "low" voltage they use the in-between states to encode more bits per cell. [1]

Yes, I'm explaining it with high and low voltage because that's an easy example to wrap your head around if you haven't thought about signal processing or hardware engineering before.

How much calculus would it require in order to get a decent grasp on signal processing? Not to work in the field or become an expert, but to gain an at least somewhat intelligent outsider’s understanding of it?

Don’t work in the field but I believe fast fourier transforms are commonplace so at least enough to have a solid grasp of that?

Most intro classes require calculus 1 & 2.

Learn what's the deal with the Fourier Transform and the Z transform. Then learn how to design some digital FIR filters. Oh and do learn about the Nyquist-Shannon sampling theorem, it's very important. And that's about it...just joking, there's tons more. But that would be a good start.

Increasing the number of bits per cell is an exponential decrease in reliability for a multiplicative increase in capacity. Flash manufacturers have become notoriously secretive about TLC/QLC retention and endurance and hope that you don't notice. Meanwhile SLC is near extinct and sells for much more than the 2x-3x-4x multiples over MLC/TLC/QLC that it should normally cost. It's none other than planned obsolescence.

> Increasing the number of bits per cell is an exponential decrease in reliability for a multiplicative increase in capacity. Flash manufacturers have become notoriously secretive about TLC/QLC retention and endurance and hope that you don't notice. Meanwhile SLC is near extinct and sells for much more than the 2x-3x-4x multiples over MLC/TLC/QLC that it should normally cost.

Yes.

> It's none other than planned obsolescence.

What makes you say this?

Even products that are built for a long lifetime of heavy use only sometimes need to drop down to MLC. Most servers and basically any consumer devices are fine with TLC.

Lack of SLC is not making drives die early.

Even on those 4-5 bit devices, the impact on performance tends to be a bigger deal than the impact on endurance. And there's no great push to get people onto those drives. TLC drives get most of the attention.

> Your storage space is divided by 2^n going from n levels of voltage per cell back to SLC

it's not that bad, it's divided by log2(n).

Those are known as pseudo-SLC, they are common in industrial applications.

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