On: UltraRAM

[Cort3z]

DDR ram is refreshed every 64ms (varies by DDR generation and specific chips). Branch Education has an excellent video on this named "How does computer memory work?"[1]. It would still take an exceedingly long time to reach a trillion, but it's still pretty frequent.

[1](https://www.youtube.com/watch?v=7J7X7aZvMXQ)

[xnorswap → Cort3z]

1 trillion * 64ms is over 2000 years, I think it's unlikely that there's any DDR RAM that old.

[Cort3z → xnorswap]

From just refreshing. You generally do other stuff than refresh the ram too.

[MayeulC → Cort3z]

You don't need to refresh non-DRAM memories though.

I agree that some regions risk being R/W more than others, so memory controllers should indeed perform some kind of wear levelling, but otherwise I find it hard to imagine trillions of overwrites across GBs (or TBs) of data. 1e6 cycles is definitely doable, and on the low side, even for flash devices. 1e9 is pretty good for general-purpose memories, and few applications require 1e12. Not even SRAM or DRAM have unlimited endurance, due to physical wear. It's hard to find a source on this, but I would probably hand wave it at around 1e15 cycles for DRAM? This would be 30 years of operation for one access every microsecond.

[xnorswap → Cort3z]

Of course, but it's still a huge order of magnitude difference to get to trillions.

[archontes → xnorswap]

Like, say, serving a million MMO users?

[Kirby64 → xnorswap]

In comparison, 10 million would mean less than a day if it was refreshed every 64ms. Even a billion would mean only 2 years worth of cycles.

I think a trillion, or at very least 10s-100s billion is the correct amount of cycles for RAM.

[mastax → Cort3z]

Persistent memory doesn't need to be refreshed though so that's irrelevant.

[thereddaikon → Cort3z]

This type of memory wouldn't need refresh so you can cut out all of those writes.