By: Heikki Kultala (heikki.kultala.delete@this.gmail.com), November 26, 2022 12:48 am
Room: Moderated Discussions
anon2 (anon.delete@this.anon.com) on November 25, 2022 4:07 pm wrote:
> Heikki Kultala (heikki.kultala.delete@this.gmail.com) on November 25, 2022 7:31 am wrote:
> > The ECC needs to be stored. as ones ane zeroes
>
> ECC can be stored out of band. Flash controllers can disable on chip ECC and do their own.
>
> Then, depending on the translation layer, ECC adjustments could be written independently,
> e.g., streamed out to the log. If you had a frequently updated page, you could keep the ECC
> in a cache even, and only write it out on power failure or when the page is filled.
>
> I don't know of if anybody is actually doing that (multi programming the NAND) or if it would
> be very useful or even possible. Programming a modern NAND is a fine art and there are all
> sorts of effects from every operation (read, program, erase) including on nearby devices.
Storing the ECC to totally separate place as the data is horribly inefficient.
Two reads to totally separate places is considerably more expensive than one slightly wider read.
And storing the ECC bits to somewhere else does not solve the actual problem - they still have to be erased. If storing them to different kind of flash memory that has much smaller erase blocks - then that memory is MUCH more expensive per bit than the memory used to store the actual data.
Making everything much bigger, more expensive, slower and more power-hungry.
That something is theoretically possible and that something makes sense are totally different things.
> Heikki Kultala (heikki.kultala.delete@this.gmail.com) on November 25, 2022 7:31 am wrote:
> > The ECC needs to be stored. as ones ane zeroes
>
> ECC can be stored out of band. Flash controllers can disable on chip ECC and do their own.
>
> Then, depending on the translation layer, ECC adjustments could be written independently,
> e.g., streamed out to the log. If you had a frequently updated page, you could keep the ECC
> in a cache even, and only write it out on power failure or when the page is filled.
>
> I don't know of if anybody is actually doing that (multi programming the NAND) or if it would
> be very useful or even possible. Programming a modern NAND is a fine art and there are all
> sorts of effects from every operation (read, program, erase) including on nearby devices.
Storing the ECC to totally separate place as the data is horribly inefficient.
Two reads to totally separate places is considerably more expensive than one slightly wider read.
And storing the ECC bits to somewhere else does not solve the actual problem - they still have to be erased. If storing them to different kind of flash memory that has much smaller erase blocks - then that memory is MUCH more expensive per bit than the memory used to store the actual data.
Making everything much bigger, more expensive, slower and more power-hungry.
That something is theoretically possible and that something makes sense are totally different things.
| Topic | Posted By | Date |
|---|---|---|
| Is 1 more expensive than 0? | Andrey | 2022/11/21 05:23 AM |
| Is 1 more expensive than 0? | Juha Lainema | 2022/11/21 06:15 AM |
| Is 1 more expensive than 0? | Adrian | 2022/11/21 07:21 AM |
| Is 1 more expensive than 0? | anon2 | 2022/11/21 05:29 PM |
| switching between 0 and 1 is what consumes power | Heikki Kultala | 2022/11/21 07:23 AM |
| Thank you all for your answers. (NT) | Andrey | 2022/11/21 08:29 AM |
| Is 1 more expensive than 0? | Foyle | 2022/11/21 08:58 AM |
| Is 1 more expensive than 0? | Michael S | 2022/11/21 10:51 AM |
| Is 1 more expensive than 0? | Captain Obvious | 2022/11/21 11:29 AM |
| obvious stuff | anonymou5 | 2022/11/21 02:25 PM |
| obvious stuff | Andrey | 2022/11/21 02:50 PM |
| obvious stuff | Michael S | 2022/11/21 03:43 PM |
| SRAM is bistable | Anon | 2022/11/21 10:50 AM |
| SRAM is bistable | Andrew Clough | 2022/11/22 05:53 AM |
| NAND Flash 1 and 0 | jokerman | 2022/11/24 01:13 PM |
| NAND Flash 1 and 0 | Joern Engel | 2022/11/25 12:00 AM |
| NAND Flash 1 and 0 | Ungo | 2022/11/25 02:26 AM |
| The ECC needs to be stored. as ones ane zeroes (NT) | Heikki Kultala | 2022/11/25 08:31 AM |
| The ECC needs to be stored. as ones ane zeroes | anon2 | 2022/11/25 05:07 PM |
| The ECC needs to be stored. as ones ane zeroes | Heikki Kultala | 2022/11/26 12:48 AM |
| The ECC needs to be stored. as ones ane zeroes | anon2 | 2022/11/26 02:00 AM |
