5 ms·

to demonstrate that the device remains stable even after 60,000s A little over 16 hours? That's suspiciously short. The endurance vs retention curve isn't clea

to demonstrate that the device remains stable even after 60,000s A little over 16 hours? That's suspiciously short. The endurance vs retention curve isn't clear from this article either; they say "10 years" and "5.5 million cycles" but it seems more like you either get 10 years and 1 cycle, or 5.5M cycles to immediate failure with no regard to retention. It reminds me of this old paper on testing USB drives for endurance, where they just hammered at the flash until it failed to program immediately and "concluded" that the endurance was many orders of magnitude higher than the manufacturer's specifications, with no attention paid to retention at all: https://www.usenix.org/event/fast10/tech/full_papers/boboila.pdf https://www.usenix.org/event/fast10/tech/full_papers/boboila...

tlb 2y ago
It's more like DRAM with a much longer refresh time (60 ks instead of 60 ms).
- IanCal 2y ago
  60,000 seconds was the amount of time it was tested for, they then extrapolate that out linearly. It doesn't need refreshing that often.
  - tlb 2y ago
    DRAM will also normally hold most of its data for 1000x longer than the rated (usually 60 ms) refresh time. This has sometimes been used to recover secrets from powered down computers. The rated refresh time is chosen to give near-zero errors over years of operation, accounting for worse-case leakage from any bit, but most bits leak much less than that.
    - wtallis 2y ago
      I think older systems also tended to use a fixed refresh rate, rather than refreshing more often as the DRAM temperature rises. Temperature sensors on DRAM are more common now, so systems don't have to be so conservative with the refresh intervals.
  - dragontamer 2y ago
    > 60,000 seconds was the amount of time it was tested for, Surely if they already have a test setup, then having a test last for 600,000 seconds isn't very hard? Things that look linear for a short period end up being exponential over longer periods. I don't think we can assume linear extrapolation here. There could be physics at play where exponential degeneration of the voltage occurs. Its a good start of a test. But it seems weird in that a paper like this would have taken much more than ~1 week to write, so making a test last ~1 week for their calculations seems within the feasibility of this group. But its oddly missing data.
londons_explore 2y ago
Even if it did have a 16 hour retention, this memory would have plenty of uses. Adding a couple of percent of ECC data tends to 10x retention anyway, so there is a direct engineering trade off between retention and capacity.
foxyv 2y ago
That would be perfect for any high performance working storage on replicated distributed applications. Stuff like Redis, Cassandra, etc... You would never turn off the power anyways. Places where you are otherwise using RAM disk or TMPFS storage.

tlb 2y ago

It's more like DRAM with a much longer refresh time (60 ks instead of 60 ms).

IanCal 2y ago
60,000 seconds was the amount of time it was tested for, they then extrapolate that out linearly. It doesn't need refreshing that often.
- tlb 2y ago
  DRAM will also normally hold most of its data for 1000x longer than the rated (usually 60 ms) refresh time. This has sometimes been used to recover secrets from powered down computers. The rated refresh time is chosen to give near-zero errors over years of operation, accounting for worse-case leakage from any bit, but most bits leak much less than that.
  - wtallis 2y ago
    I think older systems also tended to use a fixed refresh rate, rather than refreshing more often as the DRAM temperature rises. Temperature sensors on DRAM are more common now, so systems don't have to be so conservative with the refresh intervals.
- dragontamer 2y ago
  > 60,000 seconds was the amount of time it was tested for, Surely if they already have a test setup, then having a test last for 600,000 seconds isn't very hard? Things that look linear for a short period end up being exponential over longer periods. I don't think we can assume linear extrapolation here. There could be physics at play where exponential degeneration of the voltage occurs. Its a good start of a test. But it seems weird in that a paper like this would have taken much more than ~1 week to write, so making a test last ~1 week for their calculations seems within the feasibility of this group. But its oddly missing data.

londons_explore 2y ago

Even if it did have a 16 hour retention, this memory would have plenty of uses. Adding a couple of percent of ECC data tends to 10x retention anyway, so there is a direct engineering trade off between retention and capacity.

foxyv 2y ago

That would be perfect for any high performance working storage on replicated distributed applications. Stuff like Redis, Cassandra, etc... You would never turn off the power anyways. Places where you are otherwise using RAM disk or TMPFS storage.