
Ferroelectric RAM - curtis
https://en.wikipedia.org/wiki/Ferroelectric_RAM
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leggomylibro
It's great stuff, but still low capacity and high cost in commercial chips. If
you want to play with it, check out TI's MSP430FRxxxx microcontrollers. They
have FRAM instead of Flash.

Also, there are 8-pin FRAM chips with the same pinouts as generic QSPI
Flash/RAM/etc chips which you can buy today.

Again, it's still low-density and expensive, but that seems to be improving
and it's fun to make applications which can re-write nonvolatile data by word
rather than by page.

~~~
baybal2
And destructive reads with limited life cycles, assures a steady recurring
revenue for TI...

~~~
jhayward
Trillions of cycles isn't that "limited", compared to e.g. Flash.

~~~
baybal2
FRAM is far from trillions of cycles, more close to billions, which still
kills it after ~5-7 years of intense use.

~~~
castratikron
No, FRAM really is in the trillions of RW cycles.

[https://www.cypress.com/file/209146/download](https://www.cypress.com/file/209146/download)

~~~
baybal2
TI spec for FRAM is 10^10, but in real life you do feel that it's noticeably
lower.

~~~
castratikron
TI micros are overpriced anyways. The NXP RTs are way better bang for the
buck.

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evancox100
One of the benefits of FRAM is that you can put it through extreme radiation
and still have it work afterwards. So you can put it in a medical instrument
that undergoes gamma ray sterilization, and it will still not only work but
also retain the data.

~~~
jpmattia
> _One of the benefits of FRAM is that you can put it through extreme
> radiation and still have it work afterwards._

There are no oxides in the supporting circuitry? [Do you have a link to rad-
hard results?]

~~~
evancox100
I only have access to the same public info you would. Here's a technical paper
from TI:

[http://www.ti.com/lit/wp/sboa154/sboa154.pdf](http://www.ti.com/lit/wp/sboa154/sboa154.pdf)

BTW according to TI's support forum, the MSP430F chips with FRAM are not rated
to withstand the high levels of gamma radiation used in medical sterilization.

However, Maxim does have many parts rated for that type of application, with
"non-floating gate" NV memories. (Draw your own conclusions about what they
are referring to.) [https://www.maximintegrated.com/en/app-
notes/index.mvp/id/60...](https://www.maximintegrated.com/en/app-
notes/index.mvp/id/6075)

Edit: And of course there are oxides, but you can margin around the assymetric
Vt-shift that occurs in the transistors.

Edit 2: At least one part explicitly states in the data sheet that it uses
FRAM.
[https://datasheets.maximintegrated.com/en/ds/DS28E84.pdf](https://datasheets.maximintegrated.com/en/ds/DS28E84.pdf)

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mark-r
Not too many days ago someone was complaining about how posts about promising
new technology always attracts comments warning that lab results aren't the
same as commercial products:
[https://news.ycombinator.com/item?id=20753342](https://news.ycombinator.com/item?id=20753342).
I responded that countless times in the past promising technologies had passed
by without leaving a mark. Ferroelectric RAM could be the poster child for
that effect - it's been around for decades but still hasn't made an impact.

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keithnz
we make a lot of use of FRAM in our embedded systems. It's great stuff. With
huge amount of write cycles it simplifies the data structures you need to
store compared to page based / lowish write cycle memories.

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jhack
“FeRAM's advantages over Flash include: lower power usage, faster write
performance and a much greater maximum read/write endurance (about 10^10 to
10^14 cycles).”

This sound impressive until you get to the part where reads are destructive,
and reads heavily outweigh writes in most workloads. Sounds like a pretty
significant disadvantage.

~~~
kirrent
That's really not a problem just as it's not a problem in normal RAM. With
increased speed and endurance it's a doddle to write back a value after
reading with your memory controller even if you're not putting in dedicated
refresh hardware. It's really all about density and cost.

~~~
kragen
Unless you lose power in the interim. Flash doesn't have that problem, and
normal RAM has it so badly that we rely on Flash to store permanent data and
only use DRAM as an ephemeral cache.

~~~
kirrent
The first datasheet I found for a Cypress FRAM chip gives a required power
down rate of at most 30us/V which allows it to continue to provide normal
operation protecting data. It's a very easy limitation to live with and
engineers often deal with far more difficult problems in unexpected power loss
than this.

~~~
kragen
Yeah, that doesn't sound that bad. Sounds like the kind of thing that often
has subtle bugs in the implementation, though.

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LocalH
Fun fact: Sonic 3 for Sega Megadrive/Genesis used FeRAM as save RAM.
Generally, a Ramtron FM1208S-200CC. I think a few other carts of theirs used
it, I've seen 32X Virtua Racing carts with Ramtron FeRAM parts.

